She told me that didn’t want a relationship but now it’s in a formal one

I 33M had a fwb with a 27F, we starting having sex and dates for over 2 months, while she was in a open relationship with her gf 33F.I fell in love with this girl and told her and asked for a formal relationship because she was what I wanted, several times told me that she didn’t want a serious or exclusive relationship with anybody (including her gf) and that she recently broke up with her gf but they still see each other and she will sleep over at her house for days .I started to get jealous and asking for more attention from her but I was getting less and less, if I used to see her 2 or 3 times a week, now once every 2 weeks ,when texting her she will reply say later so I was not getting what i was getting during the months,so I decided to have a conversation with her , telling her that I needed more and that I will give her space , next day I went to her birthday party that her gf organized and notice that they were kind of together and they love each other , she barely looked at me at the party or talked to me so I got upset and send a message to her gf saying that thank your for letting me come to the party and that I will give them space so they can be happy in the relationship and that if I accepted to see her gf it’s because I thought you were ok with it so her bitchy reply was that she doesn’t wanna be related to my drama and to not text her again , that got me more upset and sent her another long text next day , saying that if I’m backing up of this it’s to not make her suffer and she reply even more bitchy and asked me to leave her the f!$ alone ! Then! , 2 months later , I reached out to my ex fwb on Instagram and sent her like a sex meme and she didn’t even reply , I texted her on WhatsApp telling about something that happened to me and she didn’t answer nice , and the last time I told her I miss her and didn’t answer my message . Now I found out that she is been in a serious and exclusive relationship with her gf and she couldn’t even tell me that after she told me that she didn’t want a relationship with anybody ! What should I do? I miss her and sex was amazing with her !