Boyfriend keeps liking his ex's pictures

I have been dating my bf for 7 months now. He seems to be in love with me and we talk about our future together often. I have been burned really badly in my past by multiple guys who have either cheated on me or lied to me and told me they were single when they werent. So now i am really insecure and suspicious with my bf because I go through his phone, stalk his social media accounts and constantly ask him questions to see if he is like one of those guys. He knows that I go through his phone and gives it to me willingly, although recently he got a new phone and tried to get me to set up thumb print acccess to his phone but i denied because im trying to work on trusting him. I have also cut back on social media stalking however yesterday I found myself going through his fb photos, probably because I am off from school and bored and have nothing to do with my time so i go back to unhealthy habits, and saw that he has a lot of pics of his ex gf on there. So of course I click on her page and saw that he has been liking her photos recently and it made me really insecure and upset. I ignored him last night but im sure he doesnt think much of me not responding to his texts because he probably just thought i was sleeping but very soon i know he is going to wake up and text me and i dont know if i should address my insecurity or not. If i dont, then i dont think i can pretend like i am fine. My bf has gone above and beyond to try and show me that i can trust him, when we first got together he deleted and unfollowed every “ig model” and also gives me his phone willingly whenever i ask. When i would go through his phone i found that just before we got in a relationship he was messaging his ex and their conversations were telling each other how much they miss each other and they want to cuddle blah blah but he stopped as soon as he asked me to be his gf. A part of me thinks that he does still want to be with her but he cant because she lives in a different country and they only broke up because he came back to the states. I only believe that because of my insecurity most likely but also because they didnt have a bad break up and they still follow each other on social media and were talking before we just got together and now i found out he still likes her pictures and posts. What do i do? How should i handle this?