Long story short since I'm on mobile, my girlfriend and I have live together and have been together for about 6 months - about 3 months ago she started spending a hell of a lot of time with one of our mutual friends, who happened to be a close friend of mine I've known even before I met her. Being the laid-back and chilled out guy I am I just let it happen and didn't worry about much, until I noticed little 'signs' here and there; mainly her mostly ignoring me and spending almost all her free time at work around him (we work together as well) and hardly ever being at home so she could go out and get high with him and crash the night on his sofa, or so she said, and this went on for at least 2 months. I won't go into the details about what happened then but eventually my suspicions and anxiety got the better of me and I managed to find the chance to go through her phone without her knowing, and found out they had been sexting and having an affair behind my back the entire time, while lying to my face about it and denying it every time I brought it up. She had sent him countless nude photos of herself while constantly bitching about me and how she wanted to break up with me to get with him instead.

It's been a month since that incident and we're working things out now, I've decided to try and move past it since I believe everyone deserves a second chance but I don't know, I guess I need a second opinion from you guys.