Waiting on the proposal :)

Ladies :) so, I've been dating my man for three years now. We've had our rough patches here and there but we are still going strong and so in love. As we are not married yet, we haven't started living together but see each other everyday and still do the cute things like me making dinner while he brings my favorite smoothie after a long day of work. The only thing is I study overseas which means I'm usually gone for 3-4 months at a time and caught him texting one of his exes while I was away which was a year ago and I don't think he does that anymore and sincerely apologized and makes it up to me BUT still worries me since I'm not quite done with school yet and will have to go for another few months soon. I do trust him but I get worried! I hear people say that long distance relationships often end up in break ups as it's hard to be so far physically...