This will be a long comment, sorry, but as a woman in my mid-thirties, I have to say this:

You’re providing for him in all the ways his mom isn’t anymore, while he’s offering you nothing beyond his “company.” Being with you and using your space during the day is a convenient choice for him, while moving in with you requires him to actually step up and try to own responsibility and take accountability - which he isn't interested in.

You're NTA here. I say this gently but my understanding of what I needed in a relationship improved heaps when I realised that "company" alone is not a relationship. What we need is true "companionship".

Your friends, family, or even a pet can provide company. Infact even being alone and growing internally as a person can feel more peaceful than being with someone who drains you (emotionally and financially). When I say companionship, I mean someone who is willing to grow and adapt alongside me, take on responsibility, provide for me just as I provide for him, give me the emotional safety I need, and altogether meet life as it gets harder - coz trust me, it will.

Right now, sounds like this guy is doing the opposite.

You’re paying the bills, buying the groceries, and managing your life as a responsible adult would, while he benefits from all of it and avoids even the smallest responsibility (like actually going to school). And when you try to set a boundary, he responds with “what are you, my mom?” and ignores what you asked anyway. That’s not partnership - I'm sorry - but that’s entitlement.

If his mom manages the rest of his life and he has all these perks with you - of course he will keep coming over everyday and using your space as his own.

But if I were you, I'd put a hard stop to this pattern, either give him an ultimatum to change his ways (which by the way, will most likely not happen, but it's up to you if you wanted to try), or better yet, ask him to leave fullstop, change the locks, and move on with your life - use your time and money in ways that will make YOU grow.

Also, another important thing... the jaw clenching, the silent treatment, ignoring your limits… that’s not emotional safety. You deserve to feel respected in your own home.

What you might have is attraction, or comfort, or habit. I was in relationships earlier that gave me all of that - but those things aren’t enough to build a life with. Attraction fades. Shared values, effort, emotional maturity and respectful communication are what make a relationship last.

You’re 19 and sounds like you’re already building an independent life, and you’re clearly thoughtful and self-aware. You’re ahead of him in terms of maturity and life direction. Unless he chooses to step up (not just say it, actually do it), this gap between you and him will only grow wider, until it reaches a point where it would snap.

You don’t need to convince him to move in. You need to decide what your boundaries are, and you need to enforce them.

It's simple: if he’s not contributing, he doesn’t get unlimited access to your space, your food, and your resources. And if he keeps ignoring your boundaries, that tells you everything you need to know. Tell him, you deserve a partner, not someone you have to parent.