To me, mid-college is somewhat early to propose. Maybe that's just a background difference, though. Do you feel you should be engaged to someone by now?

This is just my opinion, but if you are doubting the relationship this much, maybe it is time to cool it and spend time around other people. Maybe you'll come back to him, maybe you won't. College is such a good opportunity to meet people (especially compatible people, if you like the attitudes and/or values at your school), and it's perfectly OK to want to do that.