Should I be mad at this ?

My boyfriend and I broke up for about 5 months and I found out that during that this girl sent him a video of herself riding a dildo on sc . I really could care less because we weren’t together at the time . But I went onto his iG and I saw that he looked up that same girl on “IG “ i just don’t see why he would have any business looking her up when he’s in a relationship with me ...