my boyfriend is constantly liking his exs pictures on ig, facebook, etc.?

[Briana]

okay so ive been sating this guy for about 8 months now. hes 24 and im 21. basically ive been getting really upset about how he likes alot of his exs pictures on instagram and any form of social media basically. its not just exs either alot of girls are also just people that hes "been with" in the past. hes always trying to tell me i have nothing to worry about but it honestly really bothers me how hes liking things and they are liking his stuff back all the time. should i be concerned about this or am i completely overreacting? also these girls arent really my age theyre more closer to his age which also worries me even more. someone please help before i go insane!
also this is something i bring up to him constantly and hes already broken up with me about this. its just hard to see and it honestly makes me feel like shit pretty much.
and oh trust me i agree that being friends with exes can be okay. but i find it out how the girl will constantly like his pics on ig but if he puts a pic of me or anything that has anything to do with me they wont like it. idk it just seems odd to me.
i guess im constantly looking because it seems to always be going on all the time. sometimes its not even me finding it my friends are the ones telling me what they saw. and social media wouldnt be a problem if he would only let people know hes in a relationship. his ig shows that he is no relationship with anyone he looks pretty much like a bachelor. and for a while i didnt even have an ig because it was causing so many problems and i didnt want to see anymore of his ex lovers or hookups liking his shit and him liking theirs. he also had me blocked for awhile just so i couldnt see anything anymore. but we recently stopped that and started following eachother and its literally happening all over again.