Hi, I will try to make this as short as possible and sorry english is not my first language but i desperately need advice. 

I met my bf in 2014 and I immediately fell for him. He already had a gf of 2 years back in the day but we became close friends anyways. Until august 2018, he was with her and cheated on her with three different girls, including me. They also had a break at ont point and she slept with another guy and he was very upset about it, even tho they were on break.  Anyway, since 2014, I dated multiple guys that i didnt really like that much and cheated on them too... Last august when she broke up with him, I was there, ready to catch him. It was clear since the begining since we were both cheaters that we should have an open relationship, in order to prevent the problems cheating can cause. We didnt talk much about it except we had this one rule : If one of us wants to go see someone else, we have to talk about it first and not do it behind each others' back. 

I always believed that sex and love can be dissociated. It's not because i LOVE chocolate that i want to eat only chocolate for the rest of my life... Since he was deeply in love with his ex despite cheating on her, i thought he wanted the same thing. I asked multiple times if we could talk about the cheating issue a little more because i thought it was a bit unclear... Like what do we consider is cheating? And also, "talk about it first" is pretty vague... do we want names? do we want details? do you want me to tell you " I'm going to see XYZ tonight" or do you want me to ask for permission? Is it only with people i dont really know (tinder or whatever) or with close friends? etc... But he always brushed it of and it stayed unclear. 

I was fine in this situation because until this fall, i didn't meet anyone that would make me wanna feel like cheating. Well, it happened. There's this cute guy at work and we have a good chemistry going on. I know i couldnt fall for him and its mainly friendship and lust, but i can become pretty obsessive about new people and it was on my mind a lot. 

Well I didnt really know how to tell my boyfriend since it was so unclear and had a weird feeling since the end of october. Well wednesday we had some kind of a fight and I was angry and I finally told him that I was mad we couldnt talk about the cheating issue because right now i felt like cheating and i didnt know what to do. At the start he told me he decided he would just never cheat on me and he understood i needed it so he gave me some rules (No regular side dicks every week, etc...). But i could tell he was not being honest. He finally admitted he didnt want me to go see anyone else, that he was jealous and didnt want to imagine me like that. I told him calmly I was angry and disapointed. That it was also making me sad and i was feeling conflicted. He told me i had the right to feel angry and that he was sorry he changed his mind and should have told me earlier. 

So now I've been crying since wednesday and trying really hard not to self-harm. I'm angry and disapointed because he nourished false hope for a year and a half before being clear  with me. I'm angry because I just dont believe he just wont cheat, since he loved his ex-girlfriend so much and he did it anyways. I'm angry because I hate that jealousy is a normal feeling and i should just accept it, even tho i believe monogamy is a stupid concept. I'm angry because I'm the one who should compromise not to go anywhere while he should "win". I'm angry and I want to hurt him. I'm angry because it's easy to say he wont cheat when there's nobody in his life right now that he finds interesting. Hell, even i before i met that guy at work i was like "maybe the age of cheating is over??"  
I'm sad that I'm angry at him because I love him so much and I loved him for such a long time and I'm ashamed of reacting like that. I mean, we have a great relationship, great-ish sex life, why would I want to go see anywhere else? I feel so sad that I'm currently so conflicted I want to sabotage everything. All these feelings make me either extremely numb (no desire to cuddle, kiss, have sex, talk, look in his eyes) or just cry because I dont know what to do... So whats the point of "sacraficing my freedom" if its to continue in this relationship feeling half dead not even able to look at him...

Most people would tell me not cheating is just the right thing to do and to continue with my BF and just control my actions... I get that. Society is monogamous, I should force myself in the mold. But how do I become less angry after him and everything? After all, no one is dead, he didnt ask me anything that anyone would consider exagerated. I'm also scared if I stay in this numb state for too long he would just leave me...

Wow this is already such a long post... anyways, if anyone had any advice that could help me cope with all of this...