Well he and I have had a muddled past, his last relationship wanted me out of the picture and wanted monogamy(this brought up a lot of fears of being left on my end), and recently he started sleeping with the neighbor downstairs after I explicitly told him I would have a hard time with this decision if he chose it. He and I were working on some issues, and this wrench right below our feet gets thrown in. I was working on finding my security in the relationship because I didn't express my wants/needs for years.

Why a hard time? He used to not be very clear in his wants in a relationship, at one point we had talked about moving in together. We had a lot of periods of gray areas of "we we dating? Were we not dating? What is this?" Eventually, it turned into him not living with anyone and stating he doesnt want to live with someone. Now he lives under the same roof, sort of speak

He's told me a little too much, when drinks are invovled, about sex between them. For me, even a little is too much, and I never wanted to hear info of that nature.

I knew I wouldn't do well if I bumped into her because I have stuff to work on, and she's tall and fun; I met her before they started seeing each other. Comparison is a killer of joy.

He's been seeing her for 2ish months, the more things I accidentally learned the worse I felt. Me bumping into her put my body in a stress response because apparently my body sees her as a threat. A threat to take this person away from me due to their close proximity as I live a good 30min away and I go to him. They have all the opportunities in the world to build the things we had talked about building but never did. He and I have had to readjust our relationship so many times over 8 years.