Things are Falling Apart - next steps?

My boyfriend and I have been together for 5 years. We both envisioned getting married and starting a family someday soon. But the last 6 months things just started falling apart. He started taking an acting class and suddenly he has this whole social life that I'm not a part of. It includes cute, flirtatious single girls that he's crushing on. On top of that his brother and girlfriend started living with us (it's been 6 months) so our relationship started to feel more like "roommates" rather than a couple. He feels stressed about his career, ashamed and guilty about the crushes, and he wants to have the experience again of falling in love with someone new, even though he knows I'm perfect for him.

I just don't know what to do next. Should we take a break, give some space for things to settle and see if things work out again? See a couples counselor? Treat the relationship as if we're married and put our all into making it work? He's trying to fix things, but I'm worried we'll need a drastic change to get back to where we were before.

Thanks ahead of time for any advice. I really appreciate it.