I've been with my partner for 7 years, he's 24 and I'm 22 and I was getting a weird vibe the past month or so and I found some weird messages from a girl on his phone, basically her begging him to get in touch so they could talk about things etc but he hadn't replied and she finally said he wouldn't be hearing from her again.

I confronted him about them and he admitted that he was friends with this girl, she used to come into the bar where he works for a chat after his shifts and they spoke via txt, him talking about stuff that was going on with me and him, her sharing her problems. But apparently one night he went to hug her goodbye and it turned into a kiss, he freaked out and left and hasn't spoken to her since (hence the messages from her begging him to talk to her).
I basically don't know how to handle this, this man is my soulmate, we've been through a lot worse than this so I know I can forgive him but it's just messing with my head, and it makes it worse that I knew nothing of this girl, he says he just needed a friend that he could talk to that he knew wouldn't spread gossip around his workplace, but waaay back in the start of our relationship (the first 3 years was long distance before he moved up to be with me) he used to tell girls he was single to get extra attention, and this keeps playing on my mind. He swears that he never even considered romantic feelings towards this girl, and he has NEVER cheated on me during the past 7 years... I know that if it happened exactly how he described then I can get past it, I'm not going to throw what we have away over a misunderstanding, but it's playing on my mind that he didn't tell me straight away. He says he was overthinking and was terrified of losing me which is why he didn't tell me upfront and actually broke down in tears when he did confess about it, but this whole thing has totally messed with my head.

I don't think he is capable of cheating, and I believe that if he was looking elsewhere he would just break things off with me rather than cheat, but I think I need opinions from other people to get a different perspective. The past few weeks we have also been trying for a baby and I k ow with the past he has with his mum and dad he would NEVER bring a baby into the world if he thought we didn't have a future. The whole thing is just far too complicated and I don't know what to feel at the minute. Any advice would be greatly appreciated.