Regretting opening my relationship

TL/DR: We opened our relationship, my partner has fallen for someone, im overcome with jealousy and wish I never did this in the first place My partner and I are 21 and have been together for about 7 years. I would say we’re in an extremely emotionally close and loving relationship, but since we moved in together our sex life diminished dramatically. I guess because I was getting bored and wanted some excitement, instead of opting to sort this issue out with my partner, I suggested opening our relationship to have sex with other people. Because he has a higher libido than me, he give it a go first. And without doing any research or much thinking at all, we jumped straight into it. I assumed it would be easy and I wouldn’t feel jealous because of how strong our relationship is, and I felt completely fine when he started messaging and flirting with other people. I even encouraged him to go on a date when someone asked him out and he was feeling nervous about it. The guy he went on a date one was an 18 year old who had never been in a relationship. (Both my partner and I are bi btw) They had kissed and my partner even came home with hickey. This guy was also quite open about all the sexual things he wanted to my partner and wouldn’t stop complimenting him. My partner said he had also already referred to him as his boyfriend. After absorbing all this information, I became overcome with jealousy and anxiety. I couldn’t sleep and felt like constantly crying because I couldn’t stop thinking about them being together. I told my partner about how I was feeling, but I think my intense emotion didn’t allow me to communicate very well. He said he didn’t understand since this was my idea and he really likes this guy and didn’t want to suddenly dump him. They went on a 2nd date and I was anxious and agitated the whole time, I couldn’t bring myself to do anything to distract me. When my partner came home, he said that his boyfriend had said he was in love with my partner and wanted my partner to meet his mum and they wanted to have sleepovers. My heart was breaking. I went away and did a lot of reading about how I was feeling and how other people handle open relationships and I realised the kind of relationship my partner was creating was completely beyond my boundaries. I was hoping our open relationship would just consist of casual sex and hook ups, not dates, love, boyfriends and sleepovers. I let my partner know this but he expressed he really had feelings for this guy and didn’t want to break his heart by telling him he could only have sex with him. Also, that he doesn’t think he could have just casual sex with people and needs some kind of romantic relationship with them. He’s going to talk about how I’m feeling with his boyfriend on their next date and at least try to let me know where they expect the relationship to go. But I feel like my partner is smitten with someone giving him attention like this and doesn’t want to give it up. I feel like he has also not been as truthful and upfront with his boyfriend as he should have been about their relationship, and our relationship. I think he wants a full time boyfriend but my partner can only give him part time at best. Should I ask my partner to break up with his boyfriend, hurting the feelings of both my partner and his boyfriend? Should I try and deal with the jealousy and see where this goes? I’ve never felt jealousy like this before, I even keep wanting to check his phone to see their messages cause they text all the time. I just need some impartial advice on this situation, and I don’t know where else to go. Thanks in advance

It sounds to me like your partner has already found someone else, and is not willing to dump them. Keep this lesson in mind with your next relationship, and don't "open" it up.

Hey Well this is a very complicated. As far as I know when couples open to a relationship there are some ground rules being discussed. Like what type of relationships are ok or not. Usually people that are really ok with open relationships isn't more a jealously of sharing it's more a jealously of I want more time with that person. I have like friends that have open relationships. Sometimes it even gets confusing to me. But this is what I have been told by them. To me your not behaving at all like someone that's into polyamory and maybe you are just finding out that right now. But invading his private life it's totally not ok. And if your bf is really ok with him, it would be very selfish to ruin their relationship because you made a mistake. Still I believe that you made the correct decision in being open about your feelings with him, but I don't believe that him breaking up and dealing with jealousy are correct answers. Because it's his life and his decisions, and because jealousy in a open relationship it's something that happens but it's totally not like that. I'm pretty sure your just a monogamist, and even tho it seemed like a great idea at first at least you found a part of yourself.