Unless he had your permission to do so, I think webcaming with complete strangers or anyone, while he is in a committed, monogamous relationship with you is totally WRONG and you have every right to be against it.
Your reaction to this tells me shows a lot of growth. Your triggers are healthy! Think about how unhealthy it is for people who make excuses, or even buy the baloney that it's because you don't spend enough time together. He seems to be literally trying to place the blame on you for this. Your willingness to walk away from this toxic situation is crucial. Consider that you deserve to be in a relationship with someone you can relax with and you don't always have to be worried they're going to be secretly up to no good. So, if you take the time to heal, you can be just a little more free from the trauma you lived through.
I've been working on my issues with Attachment Trauma and it has been eye opening to say the least. Name of the therapist channel on Youtube is Alan Robarge. I recommend
browsing the videos on his channel and find what speaks to you.
Best of luck to you and I hope you can feel a little stronger every day. (hugs)
-Lele