Dealing with Jealousy in an Open Relationship

Hey guys :) So, I’m going through a bit of a situation in life right now. Over the past two years or so I’ve been transitioning out of living at home in a very toxic environment where i wasn’t able to focus on better my mental or physical health into a relationship with my boyfriend. It was a weird transition, and it came at a super stressful time with my family affairs, so essentially I ended up as the black sheep who abandoned the family. Onto the relationship with my s/o, I had a very interesting spark with hun that I’ve never felt with anyone prior, so that’s the only reason that I trusted him so much to help me leave that situation, if that makes sense. He’s a very trustworthy, reliable and stable person, but there’s a simple catch to our relationship that I really just can’t seem to get comfortable with, or adjust to. To preface, I absolutely signed up for this 100% knowing what I was getting into, so he’s not the bad guy at all, Im just looking for some advice or words of wisdom :/ He wants an open relationship, but only for him. We practice sort of traditional m/f roles, which I’m totally okay with, and for the most part since actually meeting me and cultivating a relationship he has yet to go through with anything with anyone else, but it doesn’t help that I’m a really insecure and jealous person. I try to communicate my feelings as much as I can but a lot of the time I shut down and withdraw because I’m frustrated with the whole situation. He’s an amazing person otherwise, and he’s explained his mental state behind this situation many times which i also understand and sympathize with, but coming from a childhood where sex and hookup culture was frowned upon it’s just a little hard to adjust to. I catch him on dating apps, his socials messaging other girls and the like, and I get jealous because I think “why can’t I just be enough?” It mostly just hurts because I have intense issues with self worth as it is, so It’s sort of like salt in the wound. He’s been incredibly supportive thus far with my mental health and family situation, which I appreciate more than anything, so it makes me feel even worse that I can’t just be like “i’m here, he chooses me over everyone else to spend all of his time with, i’m worthy of his time”. TL;DR My boyfriend wants to just have sex with other people and I am intensely jealous and spiteful, even though I signed up for it and love every other part of him. I don’t want to break up over this. I just want to be able to communicate more effectively, and cope with it? Just need some advice :(