How do I trust my bf more?

Recently he’s been doing things that have really lead me to thinking different theories. Yesterday I went on his phone and saw kik, he was only suppose to have it to talk to me because my phone had broken and I only had a different device, which I could get kik. But I didn’t know he still had it, I went on it and he immediately turned off his phone yet I saw multiple conversations. After, i started to get very suspicious. Later he had asked me if I wanted to look at his account so I did. I went onto his phone and it ended up he had logged out of kik, or his phone had done it. He told me he didn’t do it himself and said he’d never cheat on me and I 100% believe him but its hard to have trust in him around other girls or texting them. I had a toxic relationship a few years back and he had cheated (same thing happened to my current bf) so it’s really hard to trust him in certain citations. Help!! (Trust me this has been the best relationship I’ve ever had and I love him endlessly I wouldn’t imagine my life w/o him just need advice!!) Also he deleted the app once I asked him to, willingly.