It doesn't sound like you have been with this guy for very long ...? ...but conflict isn't a 'bad' thing, necessarily, and nothing to be afraid on a relationship unless with a constant thing without any of those issues being addressed and resolved - like if you find yourselves fighting over the same thing over and over, etc.

I would never say that you are too young to be "in love", but by your own admission, your gut is telling you something else here ...that he probably isn't for you - or, at least, giving you enough doubt to question it. And, in my experience, if your gut is causing you to ask the question, then you probably already know the answer.

Don't let this guy sway you with sugary words of love and life if that's not what you want.

You are afraid to hurt him ...that's not a good enough reason to stay with him if you aren't 'feeling' it. It's not wrong to stay with him if you are simply unsure of your feelings for him and want to give it a chance, but given the doubt you are already having, I'd say it would be wrong if you are just leading him on because you are scared of an unknown future without him.

He's your first and, as you said (which is, by the way, very mature of you), it comes with it's own amount of 'connection' that may or may not be real. If it's validity that you want, I'd say that it's probably ok - given your ages and the fact that the two of you are obviously in different life stages (he's looking to get married and settle down, you aren't) - to let this one go. Make no mistake, it's probably going to hurt - badly - but any more so than tormenting yourself with doubt now and regret later?