UPDATE (and the last1 on this topic) :
I found out she was cheating on me at least since February, with more than 3 guys.
This may sound weird, but I felt a relief.
I realized this wasn't my fault and it was her choice and there was nothing I could do.
I finally was able to smile, laugh, eat, feel at peace, love myself and respect myself more than I ever did.
I "tested" to see if I really feel better. I tried to go to the cinema w/o her, to see if I can enjoy it alone( For many years I went only with her at the cinema). Not just that I enjoyed, but it was better than the last years. It made me realize I have to be responsible for my happiness, I could chose the movie, where to eat, if I wanted coffee or not. Overall, it was amazing. I even pushed it even further. I knew she used to love frozen and not many hours ago i thought i will never be able to see that movie. But I went to frozen and it was an amazing movie, an amazing experience and I felt refreshed.
All that hate that i had felt for myself transformed into self esteem and love, because I knew I acted like a gentleman until the very end and it was nothing I could've changed.
The hardest step was to forgive myself for not being good enough to be with her. And if I didn't receive this news about her, I would still be at the rock bottom.
All of this happened so fast, I can barely remember the last few days. I smoked 22 Cigarette packs from Tuesday until now.
Overall, I would like to thank everyone for their support. W/o you guys I would've never had the power to try and find out the truth. I really appreciate your support.
If anyone still has questions, feel free to dm me, I'll answer honestly and offer whatever detail you want.
I hope this tread will help someone else one day.