I suggest seeing a sex therapist. It seems to me that your sexual satisfaction is tied into your past abusive relationship and you need to untangle that mess in order to move forward in a healthy way.

As you have discovered, simply getting yourself out of an abusive relationship isn't enough to repair the damage. And while I applaud you for trying to protect your current girlfriend, I'm not so sure that this is something that can be done by yourself.

You might begin with an addiction support group.

https://saa-recovery.org/
http://www.sa.org/