What should I do?

My boyfriend and I have been together for 6 years. We have been talking about marriage and have actually started trying for a baby. He works away for two months and comes home for a month. Early on in our relationship before he traveled for work, I caught him texting other girls and using dating sites, after confronting him he did stop. We then built our trust up again. We've even recently come to a point where we traded passwords and everything. He recently came home for the weekend before returning back to work in a city where he grew up. The other night he had told me about a dream he had where I had cheated on him. Which I have never in the past 6 years thought of doing so. Anyways I was just upset that he thought I would do such a thing. The next morning I woke up from a dream about him cheating on me. I had a horrible gut feeling that something was wrong. I immediately found myself on his social media page and to my surprise he had messaged his ex girlfriend asking when he could see her and another girl he cheated on her with, whom seem to be flirting back and forth until she prompted him to go for drinks followed by them exchanging numbers. This messaging has started the day he flew back into the city. When I had asked him before if he had talked to any of his old friends up there he got angry saying that he's only there for work with no time for any of that and that he's focusing on building our life together. I got the same answer the day I found these messages in an angrier tone after voicing my concern. Only this time he had deleted the messages. He doesn't know that I saw the messages. Is he cheating on me or should I trust his judgment that he would stop if things start romanticizing between them?
What should I do?
Add Opinion