I'm kind of in a sticky situation. Advice?

This is something that no one here can really help 당신 with as it's a rather personal decision.

It all boils down to what 당신 want in life, your own goals for your own lifestyle. How important is your relationship with your boyfriend to you? How important to 당신 are your dreams? How important are those things in relationship to one another- which do 당신 value more? Is your current boyfriend the person 당신 plan on living your life with?
Those are things 당신 have to answer for yourself.
당신 should also talk to your boyfriend about it as well. He's the best person to consult about this. If the two of 당신 care about one another, 당신 should be able to come to a consensus about it and find a solution.

And it sounds like all of this is a rather long time from now. 당신 have time to think and sort things out. What 당신 want in life might change between now and then, your plans may change 또는 something else could happen to throw off your plans- the future is never certain. So don't sweat it to much for now and just talk to him about it and see how he feels. That's all 당신 really can do for now.

Make sure 당신 talk to him.
Don't listen to some of these other guys and just up and dump him, but also know that your future is worth pursuing.

So, my 조언 is don't ask us, ask him.

Put your goals first. I don't have a boyfriend/girlfriend relationship, which means I'm free.

It's really what 당신 wanna do tho.

I pretty much agree with what 8theGreat said. ...and whatever 당신 do, don't let him trick 당신 into having sex and get pregnant. That might trap both of 당신 into a life 당신 don't want, and certainly one a child doesn't deserve.
Also, is the house his to say who will stay? I'm not saying that I'm right, but that might just be something he said to sweet talk you. I suspect that if the grandmother is living there, it's for a good reason, and she and his mom are probably not the ones who'd end up moving.
Whatever 당신 decide, I hope 당신 don't get hurt.