Fleas are disgusting, they hide in carpets, your sofa, your bed.. Anywhere.
My ex sounds a bit like your boyfriend, he had 3 cats and every summer the house would get infested.. I mean you'd put your foot on the carpet and you'd see them jumping up your legs. The lazy bastard could never be bothered to hoover up, either. I'd go round to see him and just end up trying to sterilise his house! He didn't care because he wasn't getting bitten, but I used to come out in these rock hard red lumps all over my feet and legs which itched like damn crazy.
In the end I thought sod it. If his house is infested the chances are that you'll be taking them home on your clothes too.. It's disgusting that nobody is doing anything to remedy the situation though. Their poor cat!
You can get stuff called "spot on", which works a treat. It's expensive but maybe you could suggest it?