long distance problem

We have been dating 2 years with one being long distance. We see each other monthly tho. We spent all summer together. I justcame back for the weekend and we havent been together in a month. Idk whats off but something isnt right. We are talking good, good physical chemistry but hes just acting iffy. For example he refuses to post a picture of us on snapchat together. I know this sounds juvenille but he always used to a month ago. Another thing is i am home for 3 nights and we wont see each other next month due to thanksgiving. Well hes not here with my family having dinner becauae he went with his even tho he sees then every weekend. Also he just started living off campus in an apartment we had this plan to go down for the day be alone together ect well he cancelled that last minute with no actual reason why. Lastly, i just feel something off. I know he is 100% not cheating and loves me. I leave tomorrow idk how to bring this up to fix it because everything is fine. Im just very confused and have never felt like this with him. Please someone help!!! I dont know if its growig apart of what because we are close still. I know this will drive me crazy after i leave what do i do?!