WTF SO has a secret Instagram account?

I've been married for 14 years and we've had our ups and downs, like any marriage. We have been up for a few years now and I've thought things were pretty good between us. Healthy sex life, I send racy photos when requested, watch (and enjoy) porn with him, I even do anal. Thought things were good, until the other day when my SO's phone rang and I walked it into him and noticed there was some message through Instagram that read, "Hey babe ;)" along with some hot girl's picture... I didn't freak out, I always get requests to follow me from girls looking for a man, etc. but I noticed the instagram account was not his. Huh, I thought strange. I did some investigating and found out he has a secret Instagram account that he uses to follow porn stars, etc. I was distant for a day or two and he knew something was wrong but I couldn't quite figure out what bothered me about this scenario. Eventually I came to the conclusion it was because: 1. It was a secret (WHY) and 2. These women looked NOTHING LIKE ME OR ANYTHING HE'D INDICATED HE WAS INTO. Don't get me wrong they were GORGEOUS. But I explained to him beautiful women in porn and doing the things you say you want to do to me. I feel, betrayed in a way which also feels ridiculous, but also feel inadequate and really self conscious. I'm 42, I look, I'd say, like your average 42 year old who's had two children and an emergency c-section. I just feel super crappy and don't know how to get past it right now :( Thoughts????