A Lonely, Codependent Shell of a Person. Please Help.

Thank you for taking a moment to see if you can help me. I will summarize my situation as best as I can.

Background: I was raised in a strict Christian cult, majorly repressed, and abused + neglected emotionally as a child. My parents aren’t bad people; I understand that. They’re just brainwashed individuals (victims as well) that passed on this curse to their children in an attempt to do what they thought was best for us. I’m the middle of three girls. I’m the only member of my immediate family (and out of most of my entire family) that has escaped this cult. I successfully de-converted about 6 or 7 years ago. I am 30 years old, so for most of my life, my thoughts, decisions and beliefs have not been my own, for the most part.
I am married to my first and only love + best friend of 15 years. We met through the religion, and married about 10 years ago. Throughout the relationship, many times things have been tumultuous and tragic. To name a few things, when we were teens, we fell in love long-distance, and my parents allowed this to happen. We were talking every day for hours and hours at a time for about a year until they decided they thought we were too young and needed to stop pursuing a serious relationship. Eventually they only allowed us one phone call a month, monitored on speakerphone. I was conditioned mentally to believe that this was what God wanted, and so went along with it despite moments of breaking through with my own feelings that this was wrong. My husband (boyfriend at the time) was so bitter and heartbroken that he had essentially lost his best friend + love and only got to talk to a robotic/brainwashed version of her anymore that he distanced himself emotionally from me and fell in love with someone else he wasn’t restricted from.
A while later, I finally broke free of my parents’ grasp and moved out of their home at 18 years old. My now-husband helped me get out after I reached out to him, and he moved me close to his home. Another long story shortened, he gave up his new love to pursue a relationship with me again, simply because it “made sense”. His new girlfriend lived across the country and neither of them could relocate. He ended up sacrificing someone he cared about in order to follow his family’s religion so that they wouldn’t disown him, otherwise he would have been happiest in polyamorous relationships. (Which he didn’t even know was a thing back then.) Needless to say, this caused resentment and deep-rooted issues down the road throughout our marriage, and to this day, in addition to many other issues.
Despite all this, we’ve managed to make the best of a crappy hand dealt. We’ve had great times, and we’ve had times we thought we wouldn’t make it. Lately, though, has been especially challenging.

We decided on March 16th of this year that we were confident enough in our relationship to open it up to other sexual partners. Literally one day later, ironically and unexpectedly, my husband became interested in an acquaintance from way out of state. As of today, they’ve talked every day all day on and off and every night talk on the phone/FaceTime from around 1 am til after the sun comes up. They both believe they are in love and will likely be together long term. This has jumped us from an open relationship to a polyamorous one in barely enough time to blink.

I know this may seem like a relationship topic, but in short, it is not. No, I was not ready emotionally to deal with my husband falling in love with someone else and pursuing a possible long term relationship with another woman. Especially since only 3 years ago in our marriage, he had admitted to me that he is so exhausted from taking on all my emotional problems single-handedly (an unhealthy response to trauma from his OWN childhood) that he wants away from me and out of the relationship. So I am extremely insecure and am negatively internalizing the happiness he is experiencing with this new love and the excitement and adoration he feels for her. We’ve had very little romance over the last 9+ years of marriage due to all our issues and my insecurities. So watching him be this way with someone else is killing me, and giving me lots of feelings of not being “good enough” for him.
We have also come to realize just how debilitating codependent I have been with him. I literally disregard encouraging words about myself TO myself, and only believe the same thoughts when they come from him. He is obviously wrapped up in this new relationship energy, and I feel more alone than I ever have been. I’m really really struggling, and in order to keep as much of my emotional issues off him as possible (especially relating to him) I’ve been having to process all this internally, completely alone. I realize now I cannot handle it on my own. I need professional help, honestly. I have been unable to get that help due to insurance coverage and lack of specialist having dealt with my situation - now put a pandemic and quarantine on top of that process.

The bottom line is - it’s not as much the poly situation that I’m struggling with. It’s the way I process the jealousy - taking it personally.
I’m not sure if anyone is familiar with the CSEI (Coopersmith Self-Esteem Inventory), but I scored a 7 on the scale. The ‘significantly below average’ score is 32. I’m off-the-charts low, and I believe the codependency is playing a huge part. I need DESPERATELY to learn how to gain confidence, trust and care for myself while simultaneously dealing with this extremely trying situation in my marriage, all while a global pandemic is wreaking havoc (and I work in a hospital, of all places).

Thank you soooo much for any contributions and encouragement.