Most Helpful Guy
I've bin there . . . different pursuit . . . for me it was going to uni . . but I think I understand where he is coming from.
First off, I think it best to get this out of the way - his texts are NOT a reflection on you.
Your looking at a dude in self reflection - he, at one point in time, was convinced that going to the gym, working out, being concerned with what he ate and so on was an investment in himself . . . and he's right.
But just me being focused on improving yourself by going university, spending lots of your time focusing on improving yourself physically can sometimes feel like a rather selfish activity.
Its totally about you, it takes a lot of your time/attention/focus and can sometimes FEEL as though its coming at the cost of other things (work/friends/family/girlfriend ect.) - thereby making a guy feel guilty sometimes that he may be becoming predictable/uninteresting or boring to the person he is dating.
Only you know if his insecurities are founded - and only you can reassure him - or - let him know if his priorities need to change.
But, as far as I can tell, you seem happy - good for you - but do the kid a favor and let him know - he wouldn't be self conscious about how he is as a boyfriend if he didn't give a sh*t about your relationship.
anyway that's enough out of me . . . take care :)