Boyfriends ex

I've been with my boyfriend for nearly a year now and I really think he's the one, ya know? We talk about how we're going to get married alllll the time. I just have one problem and that's his ex. He was with her for five years and I guess I feel like he loved her more or that she's better at giving head than me or she understood him better or some shit like that and I think about her all the time (I counted last week, I thought about her 32 seperate times in one day) and I had a dream that she was in the other night, and I already have mental health problems so every time I think of her it just makes me extra extra depressed. I also have this weird pride complex so I can't tell my bf about any of this. Does anyone have any advice about what I should do? I really need to do something about this, if I don't I think it will tear me and my relationship apart

And here's a cute photo of me and my boy