3 Months on my ex is dating my best friend. Is my anger Justified?

So as the title states, my most recent girlfriend of 3 years is now dating my old best friend, 3 months on. To add more context for u I will explain the situation a little more.

Me, my ex and my friend have all been apart of the same friendship group for a while, and that's how I actually met her. Things weren't working out so we broke up after 3 years in February. We did have a tough breakup and we did get into a few firey text chains for a bit after our breakup. A few weeks after this I noticed her and my best friend getting much closer than usual and talking a unusual amount, this initially put me on edge but I tried not to go into too much detail as to be fair he is friends equally with both of us. Unfortunately things did escalate from there and unannounced to me they were visiting eachothers houses (v unusual for them). My whole group met up a few times since then and always those too would clearly be together and passive aggressively exclude me. At this point I was feeling very betrayed and I confronted the pair, to get the response that Im crazy and that there just friends.

Stuff settled down since until about 3 weeks ago when they announced on FB they were in fact dating ( my friends had to send me this as we blocked eachother).

So right now im feeling overwhelmingly angry and betrayed, so my question is am I justified in feeling this way or am I just being oversensitive/crazy?

I feel like doing it behind my back and even trying to make me look crazy from it made things somehow worse. Its needless to say I wouldn't be able to maintain any relationship with either of them now and I do question our friendship we had before.

Any constructive comments are very welcome, I thank in advance.
3 Months on my ex is dating my best friend. Is my anger Justified?
Add Opinion