I am 26 M. About 3 years ago my 5 year long relationship ended. It was a quite toxic one and I have this one moment that is fixated is my mind now and has me in constant state of panic.

When I got involved with this girl, she did not have any sexual experience and was very reluctant at first. After a lot of talks and slow progress we started getting intimate. This was my first relationship so I was constantly charged up all the time, but looking at her reaction to the moments, I used to pull myself back. After about a year into the relationship we started trying to have actual sex but it would cause her pain and she used to ask me to stop. This happened for a very long time after which my sexual drive had started getting effected.

About 3 years into the relationship, it was the first time we had sex. Wasn't really upto expectation but I was happy we finally did it. When we were going to go for round two, I could perform for some reason. I was just not having the excitement that I wanted to. This is that incident. We talked about it she said it's okay it happens.
After this due to many reasons like distance and her being unreasonable we broke up.

During this time, she was already involved with one of our mutual friends who was in college with us. I was being lied to all this time. Long story short, that guy and me are good friends now and are part of a group. 

Yesterday we all friends met and we were discussing what kind of asshole she was where the guy said that she had also told him that I couldn't perform. She used the word 'impotent'. This issue has happened only once and I am very insecure due to it because of my anxiety issues.

Although everyone was kidding when we talked about me it hit me like a storm. I have not been able to do anything since I got home.

I am actually ready to settle down now but I am very insecure and afraid because I keep thinking what if this happens. My anxiety has reached a point where I feel nauseous and I shiver. I really need some help to get past this.

P.S. - I have been sexually healthy and active in the past year. I have had amazing sexual experiences where I was enjoying my life to the fullest. It's been a dry spell the last 10 months and all these thought are starting to creep back. And yesterday just fucked me up completely. 

I would really appreciate any genuine advice I get to have my stability back completely. Thankyou.