New To RA, need guidance

Hi everyone, I feel weird posting about a lot of personal things but I'm hoping its a friendly community here that could offer me suggestions as I'm new to RA with my partner (BPD) of 3 years, we were strictly mono till she had a breakdown finding her true self, and i fully support her and love her completely. She is fully into RA now, as it complete speaks to every aspect of her feelings, and I like the idea of opening my mind and evolving our relationship to insure our love growth and happiness. The problem is I've always been a standard monogamy relationship kind of guy, I'm scared that we will find out we are not compatible on a few fronts but i continue to want to change. She is asexual, I thoroughly enjoy sex and need that as a bounding connection...so she tells me to find another where i can get that from....well i don't want to be with anyone else physically/mentally then her. Is this a situation of me opening up more, or is this usually not going to work between a basic monogamy person and asexual poly in RA? I have PTSD from all my previous relationships of unfortunately been cheated on via sex so that lingers in my head of thinking she is having sex with other people yet i know she isn't. My partner is a loving ball of energy and i fully understand she has a lot of love to give and wants to give to others beyond myself. Is there anyone else who is monogamy that is in a similar situation? I feel like alot of this issue is getting my head/mind right and open up to this whole new experience. Me and her have had such a good 3 years together but i don't know how to handle this so if anyone has any helpful information i'ld love to know it, as I want to open up and let go of my insecurities with jealousy and just love but i feel like maybe i'm not strong enough. Sorry for the long and scatterbrained info.