How to deal with being paranoid.

Hello everyone! So I'm looking for any tips and advice on how to get over my own paranoia. I'm dating this truly wonderful guy, but I'm constantly worrying about him cheating on me. It's the same every time I date someone, and I feel this time it's worse cause we live over 100 miles away, so every weekend he's not with me I'm basically just thinking 'oh well he's sleeping with someone else' and I hate feeling that! We had a very brief conversation about trust and how it'll work cause we're far away, and I said 'I worry that you're gonna be at a pub (I met him at a festival at a pub and he goes quite often with his mates) and you're gonna chat up some other girl and take her back' and he replied 'no, no once I'm with someone that's kind of it'. And I can't say it was completely reassuring! I'm not sure if I should bring it up with him again and say it out straight that I have issues about being insecure and paranoid. Or if I should just deal with it myself and try and find a way round it! I don't like feeling like this, I want to trust him I'm just not sure how!

Thanks for reading, sorry this is a such long post 🙈 any advice and stories of similar experiences would be appreciated! ❤