Does he still have feelings for his ex? The first year we went out, he never really liked any pictures of me on social media, nor did he post anything. He told me he wasn’t much of a social media person, and I believed him. After having some doubts later on, I looked through his phone (I know that was bad), and saw that he liked two pictures of his ex about 6 months ago and has repeated searches for her name. They haven’t been together for the past three-and-a-half years. He has liked pictures of other girls as well (in bikinis and such), but refuses to like any of mine. We are long distance, so I figured social media is a good way to feel connected. I confronted him about it. He said he has no feelings for her and that he was just being stupid. So I asked him to cut her off on social media. He seemed so hesitant, but finally did it. My gut tell me something is up.
LemonVibe 
Something is up and he’s probably not all that into you. You may be in his rebound relationship.
Got bad news for you. Forcing him to block her backfires. Being controlling never works. If he had suggested it then did it that would have worked out in your favor. Now he will just be sneakier and start looking for a out.
Trust is very important in a relationship. I understand how you feel. I get knots on my stomach just thinking about what you are going through. My opinion is he might still be into her if he is going out of his way to look at her fb page.