sleepover problems

So I'm 22 (going on 23) and my boyfriend is 24 and we have been together a year now.  I live in my grandmother's house while she travels (which is 3/4 of the year) and my boyfriend still lives at his mother's house.  He sleeps at my house when possible but I am not allowed to sleep at his house because it is his mother's rule and I do not understand!!!!! I don't think she likes me.  Mothers from my town BEG for me to date their sons and for some reason this woman gives me a bad vibe.  Also to add to this, my boyfriend does not have a car so I have to drive to his house to pick him up then drive him home the next day before I have school, work etc. and it is really exhausting which is why I would like to be able to stay at his house.  I was able to stay at my boyfriends house when I was 16 years old in high school.  I really just don't understand.  They are also 100% Dominican so maybe it's a cultural thing??? Ugh I dunno someone please help me fathom this.