Firstly, welcome to PC.

Secondly, regarding the mother and sister of your BF. Do they contribute in anyway to the household? If not, consider asking them to pay rent. You are not obligated in any way to give them room and board for free. I know you're a sweet person and want to do so out of the goodness of your heart, but they are taking huge advantage of the situation. It's not good for your budget, or your mental health. Tell them to either pay rent and contribute to the household like they should have from the beginning, or move on out and find another place to live.

Regarding your boyfriend himself, trust is a huge part of any healthy relationship. You have to place trust in your boyfriend that he is going to be faithful to you, if a monogamous relationship is what you both agreed on. Keeping a guy on a short leash will make them more likely to want to leave the relationship. Give him some faith. I'm sure the texting was innocent.

I also sense you feel guilty that he is giving up so many of the things he wants to be with you. Guilt can be a powerful thing. I would have a nice long discussion with him about what he wants for the future, his future and your future together as a couple. If you two aren't on the same page, then you may not be as compatible as you'd like.

If you haven't already, find a therapist and discuss your feelings with them, and how you can deal with your issues. They can be a huge help when you find one you really click with.

Anyways, I hope you're okay and dealing with things well. Take care!!