I've recently found out that my DH of 11 months has drunkenly kissed a work colleague on three separate occasions. I've known OW as his colleague for a few years and have had a few nights out with her, and I've always been wary of her because I could tell she fancied my DH - flirting with him, spending all night talking to him, and making sure she had moments alone with him. I found out about the kisses because he'd met up with OW in secret that day for lunch (apparently for the first and only time) and I saw messages on his phone from her (one of them saying she loved him). He finally came clean when he accidentally sent me a message that was meant for her, telling her that if I rang her 'to not mention anything about the kisses.' I was obviously hysterical and I made him call her with it on loud speaker and I listened to her saying to him, 'have you told her that it meant nothing? You shouldn't lose your marriage over this.' As the last few weeks have gone on, I have found out that they used to text each other a lot and that he used to delete them because he knew I wouldn't like it. He also admits that their friendship became too close and he spent a lot of time alone with her at work. He has done everything in his power to make me believe he has no feelings for her and the whole thing was just friendship and drunken mistakes.
I have forgiven him and want to now move on, but I keep wondering if I am being a mug to do this? I also am now 100% consumed with paranoia all the time, wondering what he is lying to me about now, and whether he's lied about his feelings for her, and it is becoming physically and emotionally exhausting for both of us because I can't seem to move on and am anxious all of the time. Our relationship used to be perfect and I worry that we will never be happy again because I cannot forgive and forget after being so hurt.
What do I need to do to get over this paranoia and forgive? I am at a loss :-(