Getting over jealousy

Okay so I’ve been dating my boyfriend for a year and it’s been great minus my jealousy issues. He has past friends that are girls that he doesn’t talk to often but it worries me.. every so often they will snap chat him or reach out. One time this particular girl came to his work with her baby and brought him coffee just to chit chat 🙄also anytime I try and get to know his ex wife a little ( for the purposes of trying to have a good relationship with the mother of his son) She is sure to mention any of his past relationships including theirs, faults and who he’s slept with. I feel like it consumes me sometimes and I get very anxious thinking about it it. I was with my ex husband for 12 years yes that’s a lot of past but it was one person who frankly I was not happy to be with most of the time. I need to get over the jealousy and try and not think of those things but I feel like I’m learning this much too slowly and I fear my relationship may suffer bc of it. I have complete access to his phone and he’s very transparent but we all know things can be deleted lol obviously I have trust issues as well. Please help ladies !