Relationship advice

Okay so my boyfriend and I have been together for almost 10 months and his ex has recently tried to get back in touch with him.. she does this every few months and I know he would never go back to her but I also know he’s way too good for me and she’s so beautiful and I’m just bleh. But now I can’t get the image of the two of them out of my head and now she’s gonna be going to our college and I have no clue what to do. My bf and I don’t fight and I don’t want to seem like the over jealous girlfriend but I want him to block her number and I’m just paranoid and I’ve been waiting for the other shoe to drop since the first time we went out. I have no clue what to do