Trying to overcome trust issues...

Hi ladies. I am looking for advice on how to overcome my trust issues. I haven’t had good luck with relationships in the past. All my previous boyfriends weren’t loyal, and I had never been the jealous type, and I wasn’t threatened when they talked to other girls. My ex’s ended up having sex with other girls behind my back. It took a toll on my confidence and trust. I thought I wouldn’t date anyone ever again. Then I met an old friend that quickly turned flirty and then after 3 months talking and flirting he asked me to be his girlfriend. I was hesitant at first but I definitely had a crush on him. He told me “it doesn’t hurt to try this out.” He has been amazing! Unfortunately, I have a jealousy problem because of my past. He knows about my past and reassures me he won’t do that. I believe him, but I feel jealous when I see him interact with other girls. I think back to when my ex’s cheated on me and I just get worried and depressed watching him interact with girls. I feel this way even watching him give them any positive friendly attention. How can I overcome this jealousy? I am working on loving myself but I just can’t seem to get closure and I’m scared it will ruin this relationship... I’m in a conflict with myself and I would like to get out of this depression that I am feeling...