Oh god alive, yes you have to sort this out right now!!
Give notice to your tenants, move back to your house and wait it out.
Your BF is a mummy's boy and he's not going to leave without a shove.
Don't wait until the baby comes, you will be tired, sleep deprived hormonal and possibly unable to take this kind of battle on as a new mum striking out on her own.
Take the, this is a more realistic and grown up approach to parenting approach, Tell them how it's essential for a mum to be to feather my own nest. Tell them you have to get it ready for your DC. MIL has made it damned difficult for you to settle in and BF hasn't stood up for you.
The fact he's not pressed marriage is telling too. It's so much easier for you to be dismissed as just a GF when you are not married. Once you have had the baby and are trapped/hooked whatever, believe me any power you thought you had will have been utterly vaporised if you continue to stay in this situation.
They have created an arrangement where you are not able to feel at home in MIL house.
Tell them this and also that you are not blaming her for this, all living under one roof is highly unusual and will ultimately never work, so you are doing your bit to establish the foundations of your new family, and sorting out your accommodation.
BTW, you are not asking him to move to make you happy, you are expecting him to raise his game, to step up and be a man and the head of his new family.
FWIW, i think the MIL is potentially more manipulative than you give her credit for. And your BF is dimmer/manchild than you think.
I don't think it's laziness, it's paralysis, inability to let go, grow up and be a man. His mother has not raised him to be a father, a husband. She has raised him to replace her husband... [ew]