I do feel sorry for the lodgers. Not a lot, and I feel a hell of a lot sorrier fly you.
But from their point of view - they're paying their money, happily living in a shitpit that their landlord is totally relaxed about. Next thing, landlord's girlfriend moves in, changing the dynamic and leaving notes about plates and cups that they (and their landlord) cannot be arsed about. And now on top of that, the girlfriend is pregnant so they must know they're either going to get told to go or they're going to be sharing with a baby. Total change of dynamic and probably being woken in the night.
Now - shit happens, life changes, renting is insecure - lodging even moreso. So my heart isn't bleeding for them. But if they were my friends telling me about a girlfriend moving in, being fussy (compared to their landlord) and now there was going to be a baby? I'd say "oh no - bad luck mate!"
These lodgers are not the problem - your boyfriend is.
Because when they move out, you're still left with a dirty boyfriend who didn't care about you enough to sort this out. That personality is going to resurface in other ways
You are very vulnerable - as others have said, speak to your midwife, and look at your housing options.
This baby wasn't planned - so your boyfriend is not prepared at all, and may not care about getting prepared 