Actually....your situation sounds like the one I was in. I used to be in a relationship that I thought was ok....but....I did not get along with his family. And, I was not in school....I was doing something I didn't want to do....and I had no friends around.
Once we broke up, I felt better. I think it was actually just the relationship.
But, since you said that you have family members with BPD....you should get checked out..just in case.
It actually sounds like you're making smart choices when you have days off and when you don't. Basically, the doctors say that people with BPD stay up all night...and get no to little sleep. But, you only get little sleep when you have a day that you're working. When you're off, you may stay up late....but you sleep late as well...because you know you can.
To me, that sounds rational. And, there's very little room for being rational when you have bipolar disorder. (or when you are showing symptoms of BPD)
You could just be extremely stressed...and probably depressed since you did a life-changing thing....and since you don't get along with his family.
Don't make a big deal about the fact that your family members have bipolar disorder when you go to the doctor. If the doctor thinks you have it, then he or she will see it when you describe your symptoms. Yes, because you have family that has it...you will be apt to have it. But, that's not always the case. And, sometimes doctors will just say "Well, it's obvious what's going on here..." and just slap you with the diagnosis without really digging any deeper.
Just..go see someone about it. Maybe it will make you feel better.