Long read...

Really needing some advice right now.

My fiance went out on Saturday night with a buddy, he left angry after having argued with me early in the day over something minimal. Pretty late into the night I start getting this guy feeling that something was up. I ended up looking at his FB on his laptop, I have never looked before but this feeling wasnt going away, only to find some messages. There were about 7 different girls that he messaged or was talking to, with 1 being an ex, 2 being ones that he had an interest for at one point and 1 supposedly being just a friend. The messages to the ex were nothing major, just asking to come help him get his truck unstuck from the snow. The 2 that he had an interest in he had informed them how he felt toward them. Stating to one that he regrets things not working and he wished it had and the other he apologized for trying to prove himself and ending up pissing her off and when asked if he still had his fiance he replied stating yes but I knew you before I ever knew her. The last girl that was just a friend he kept trying to get to come back to his buddies place saying he wasnt tired and his buddy was asleep and it would just being them and what they did was their business.

I planned on waiting to say anything to him if I did at all until the next day when he came home. However, the following morning I checked his messages again and while texting me he is texting a prior fuck buddy. He was telling me that he was up but was gona be awhile before he left his buddies house because he was trying to get woke up and to get his back to stop hurting. He said he would let me know when he left his buddies and was on his way, and told me that he loved me and couldnt wait to get home. While texting me he is texting his ex fb making plans to come to her house to hang out. I'm reading his messages yo her while talking like nothing is up to him. At this point I'm shaking I'm so mad so I decide that I'm going to confront him at her place. I utilize snapchat to track him and catch him in the act. Since then he has apologized numerous times and swears he will change. He has told me that if he had been sober this never would have happened but if I didnt already find it and confront him he would never have told me because there would be no point.

So now I'm left trying to figure out what to do. I have tried talking to friends and family but feel like I need advice from someone who doesnt know me or him. What are your thoughts??

Does the punishment fit the crime if nothing happened outside of conversation and this is a first offense??

Update:

First off, thank you for the support and feedback. I knew what was needed but needed to hear it from people outside my circle.

So I have put in an application for an apartment and paid my fees just waiting for the day I can move.

I had a few discussions yesterday with people I trust to be honest with me and it left me in the fence and needing 1 thing to sway me. Today I decided to reach out to a chic that was in the picture back in May. Long story short he got her number, we split up in May, they hooked up and we ended up getting back together. He told me it happened 1 time, it was at her place and he no longer speaks to her. He was upfront and told me that it happened after I asked when we got back together but was limited on details. I moved past it and trusted him as much as I could but I have always wondered if what he told me was true or not so today I got the nerve to reach out to her. Some details she gave were the same as what he told me but several details were different. He is currently at work but messaging me so I gave him 2 chances to be honest with me, I asked him questions without him knowing I talked to her, and he is still choosing to not be honest. I plan to sit down with him when he gets home and ask him the same questions again and when he continues to lie to me I will inform him that I talked to her and I know the truth and that I am pending keys for my new place. Then I will begin packing my bags!