@Ultra Silvam Hi! I see that you are fairly new to MH, and so firstly, I'd like to greet you and officially welcome you to the site. Thank you for joining us here on MH, and furthermore, I appreciate you being open enough to share your experience with us.
To answer your question in general - no, there's absolutely nothing wrong with asking that question. That's generally something you'd want to establish prior to embarking on a relationship with anyone.
Now to address your situation. I'm going to be straight-up with you. I won't presume to give you any advice, but I will relay to you the truth as I see it, based on the information that you've provided. I apologize in advance if my comments seem harsh or insensitive, but I assure that is not my intention. I empathize with you because I've also been in similar circumstances before, and I know how it feels. So with that in mind, it's my hope that something I say will help you to avoid unnecessary heartache in the future.
There's no easy way to say this, but this guy is not looking for the same thing you're looking for. He said so from the jump:
This is all code for "I'm going to waste your fucking time". Two things to look at here. #1: He said he "didn't mind" - not "I want to" - showing that he doesn't really care either way. That's NEVER a good basis by which to approach an intimate relationship. If he's not intentional, it's very likely that he's on some bullshit. #2: He said he "wasn't looking for anything serious". What does this mean? What's the point of entertaining a relationship if you're not going to be serious about it? He's basically telling you in so many words, "yeah, I don't mind hanging out and having sex with you, but don't expect me to commit to you". aka. He's going to waste your fucking time.
If your heart is important to you, it's absolutely worth guarding. It's not something that should just be handed out to anyone. You want to be with someone who is intentional and serious about guarding it. Not someone like "i don't really care either way", ya feel me?
Some more things to look at:
Words are something else, right? The right ones will make you feel all giddy inside and send you over the moon. Here's a general rule of thumb about people: Listen to them intently. Most people will tell you who they are without even realizing it. But words can also be deceptive. So more importantly than listening to people, you also have to observe their actions and see if they line up with their words.
Check this out. He tells you "he likes you" and reiterates the fact that "he isn't looking for anything serious", but then he proceeds to have "unexpected" sex with you? Many unexpected things happen in life, but sex is never one of them (unless it's rape). Conventional wisdom won't tell you this, but contrary to popular belief - sex is actually quite serious. Let's examine your own words again:
This world will quickly sale you on the idea of 'casual sex', but I don't believe there is such a thing. And just because it's "the norm" doesn't mean it's functional. Here's why: Sex cannot be divorced from emotion, or family, or responsibility, or respect, or children, or love and so on. The idea of 'casual sex' would have you believe that it's just some standalone act done for fun and pleasure, but sex itself is innately intertwined to too many other critical components of life for that to be so. Your own emotions are a witness to this truth. So it's no wonder that you've developed such feelings for this guy as a result. You've engaged with him in a deeply intimate manner. But it's all good, don't beat yourself up about it. Just know that these things are bound to happen when being intimate with others. So you have to exercise due caution in this area. If a guy is willing to have sex with you, but is not willing to commit to you - what does that say about this guy? And what does it say about you that you'd allow such a guy to have sex with you? There's absolutely NOTHING wrong with having standards. In this world you'll need them.
Let's continue:
If I had to guess, "busy" is one of the biggest bullshit excuses ever used. Some people do get genuinely busy, but even if they do, they'll let you know that they're busy. You won't have to guess. Likewise, If someone is truly into you, you won't have to guess. Trust what your gut is telling you. You probably already know what the deal is, but whether you want to believe it or not is another story.
A bit more:
I'm going to address the text that I highlighted here:
It seems to be me that you're giving this guy way too much leeway to walk over you. If he can't be arsed to communicate with you regularly, what makes you think it will get any better down the road if you WERE to enter a relationship with this guy?
"I'll hang out with you, but I don't know when" - Damn, this guy must be the BUSIEST GUY IN THE WORLD HOLY SHIT!!!! His schedule is just THAT jammed pack that he doesn't know when he'll be able to kick it with you? Fuck outta here bro. This guys is on bullshit and is just stringing you along.
If a guy really likes you - he's going to MAKE time for you. It's as simple as that.
I'm really sorry that you're going through this, and you'll have to excuse my bluntness, but I think the real questions you should be asking is "why am I allowing myself to be treated like this?". "Why am I fawning after someone who has clearly demonstrated that they don't value me?". Seeking the answer to these questions will likely yield you better results. I believe you already know the answers to the questions you want to ask.
Now obviously what you choose to do is completely up to you. There's no harm in expressing your feelings to this guy, but based off of what you've told me so far, he seems highly unlikely to truly reciprocate.
Personally, I think you'd be setting yourself up for undue heartache and should just leave this guy alone before incurring further damage. He's already made it clear where he stands - and several times at that. Furthermore, his actions have solidified that stance. Take heed to yourself, because I know from experience that we often get lost in the clouds and make the mistake of projecting our own needs, desires, and fantasies on to other people instead of looking directly at what's in front us, and facing reality. In doing so, we often break our own hearts.
Once again, I apologize if I was a bit too coarse with my words, but I do hope you can glean something from this. And if not, that's fine too. Whatever the case, I hope that you're able to learn from the situation - whatever the outcome - and move forward in a good direction.