what is my ex thinking?

hello!
Well my boyfriend and I broke up about 4 months ago, barely had any contact in that time (we were on summer vacation), we have now come back to university and he is acting rather strange. In that he broke up with me because he'd "fallen out of love" (we were together for a year), said he still wanted to be friends and said he doesnt regret anything about our relationship.
But very recently he's deleted almost all of our online photos together and is basically being really odd, he avoids me as much as possible- doesn't seem to be able to look me in the eye- at socials he gets VERY drunk- which he never used to really do and just watches me from across the room- like proporly gives me evils if I look at him, other wise just keeps looking over and staring. If I try and say hi he ignores me or acts very ignorant indeed, my arrival is his cue to leave - or retreat to a safe distance.
I have done nothing wrong as far as I know, just wondering if any guys could shed a light on his behaviour...?

I'm slightly worried that it might be something I'm doing- I have made it clear that I do not want to get back with him, but I am still being friendly- ie if we happen to be in the same space I smile, say hello etc but I never seek him out purposely - I'm trying to give him space.
Any thoughts?
Thanks

He regrets breaking up with you but is toooo immarture to apologize and get back with you. I pity the fool who passes over a good woman. Don't stress to much over this guy, he's trying to mess with your head and be a douchbag to you so you can feel as bad as he does.

He's no more into you and he's making that very clear.
By getting drunk probably just wants to have a good time for times to come and not think about commitments and girls.
Guys are stupid just like that for no reason. Enjoying life. I'm a guy too.

he's just trying to get over you in his own ways.

try to be more passive when you see him. . . maybe some eye contact and a nod, but no speaking, etc

don't care, don't stress . . .move on.

I really dont know whats going on his head :( sowwy though.