seeing bf after being with other people

okay so my bf and i were together for 3 years or so and broke up about 6 months ago but ended on good terms. we still talked every day and hung out but we were also talking to other people. well we decided that we are gonna start talking/seeing each other exclusively again. i didnt do anything sexual with other guys during that time but he recently told me a few people he’s been with. we were each others firsts so i’ve always been comfortable with doing things and trying new things with him but now that i know he’s been with other people it’s hard to not think i’m being compared to them or maybe he’s imagining them when he’s intimate with me. i really don’t want this to be a breaking point for us because i know it’s something most people wouldn’t see as a big deal & most people have probably been with more than 1 person. but it’s hard for me to do anything with him without my mind just constantly ruining the moment. PLEASE give me some advice on how to get over thissss