Uncertainty in a 4+ Year Relationship

My boyfriend and I have been together for a little over 4 years. Practically my entire college career. Lately we’ve been hitting some serious bumps in the road. Considering we’ve been together for over 4 years, we’ve talked about marriage. I was all for it, but now, I’m unsure.

For starters I’m realizing he has a hard time committing to things in general (work, activities, goals) and it’s alarming. Secondly, sex is good but lately I’m not interested and it makes him upset. I don’t feel a pull in our relationship anymore. If I don’t feel that now, it worries me for if we were to get engaged. Finally, I’ve noticed we differ on a lot of our beliefs which makes it really hard to support and discuss worldly/life issues together.

I’m super conflicted. Whenever I mention activities for us to engage in relationship building, he’s never interested. He has a hard time with communication and I’m struggling. I’ve considered taking a break, any advice as to if they work? Or if they strain a relationship further. Help!