<human>: Can you succinctly summarize the text in 1-3 sentences?

Our bedroom has been cold over the past year (due in part to my anxiety meds, busy schedule). We both love each other very much and have a great relationship (other than the lack of sex). She has been talking about "opening" up for awhile and I finally gave in. Sex is a pretty big physical need for her and there was an opportunity for her to have sex. With concerns that the opportunity wouldn't last forever, I agreed to allow her to have sex with him before I was 100% okay with us being open. She had sex with my permission and now I'm feeling very sad and I'm not sure why. I know it's just sex, but I feel crushed. Any advice, encouragement, similar experiences, or help explaining this sadness will be greatly appreciated.
<bot>: Thought I was okay with open marriage, hurt after wife had sex. Is this normal/what should I do now?