I don't think him taking off like that on a frequent basis is normal social behavior for a guy living with a woman in a committed relationship. That may be normal for a completely unattached guy, which he is not. I think you have a right to resent it.

Then, again, if you are both young and have no children yet, I don't think he should have to sit home all weekend. It would seem to me that you both should be going out together a couple of times a month.

I went through something like you are describing, but it was due to my guy having a serious drinking problem in the past. You might want to consider whether your boyfriend is over-involved with alcohol. Staying out as late as you describe sounds like binge drinking.

As a poster above already asked, is there some reason that the two of you don't go out together to meet his friends? If he's going out to meet a mixed gender group, seems like you could go too. If he's out - without you - drinking in the company of female "friends," I'ld be worried that could lead to infidelity.