I don't think this is that bad. You were teenagers when you started dating (albeit he was legally an adult). Has he been in school the majority of your relationship? If so, it's unrealistic to expect him to be able to afford his own place - some can, many cannot.
Even if he wasn't in school, most young adults can't afford to get their own place. 24 seems about the right age to me. As for the sleepover thing, it may be a case of "my house, my rules". It doesn't sound like it's been a sexless 6 years so don't get caught up in the wish list.
It's hard to tell what your complaint is, OP, because if you were not in the same situation he was, why couldn't he have slept at your own place?