Never thought I'd catch feelings for him

This one is a taboo, messy, and an interesting one that has made me think of this forum and return back to it, as with my other posts in the previous years, I'd like some opinions on it. And at this point, I'll take any perspective, as it's been quite difficult to bring this up with any of my friends (for obvious reasons) Just to note, this is all highly condensed for obvious reasons as well.

A couple of years ago, I met my best friend in high school. Her and I hit it off pretty quick, and she has been a sister figure in my life since. During this time period, she also met her boyfriend, whom she is still with today. Because my best friend and I were close, I started to get to know her boyfriend as well, albeit slowly. Over the years, we kind of became a clique, it was always an interesting dynamic. Yes, I did feel like a third wheel at times over the years, but not in a strong way. So to speak, they rarely ever made it feel awkward if it was us three hanging out. We called ourselves, "The Trio".

Her boyfriend, we'll call him "Nick", him and I... it's hard to call us "friends", and I say that because I don't know how exactly to describe our "relationship". When I first met Nick through my best friend, we didn't exactly become buddy-buddy right away. He was standoffish, aloof. We hit it off quite rough, actually. We had a couple instances where we were all drinking too much at various parties and he would become vocal about how he felt towards me -- mocking me, making fun. But this didn't last for very long, obviously, as my best friend saw how it would make me feel. Along with that, as the years went by, we began to warm up to each other. Or should I say, he began to warm up to me. Eventually, my best friend moved in with him, and so seeing my best friend = seeing Nick. Let's just say they unironically became hip-to-hip. (seeing one person meant always seeing the other)

As the years went by, things became smoother sailing for us. We arrive at the time where we considered ourselves a Trio, he got along with me, and I got along with him. Hanging out as the three of us was always a great time, and we have made many great memories together, and with our other mutual friends. Things got a little sticky once him and I started to get along. Nick and I found ourselves having a lot in common, perhaps more than my best friend and I did, admittingly. Over time, I found myself feelings things for him here and there that I ultimately kept suppressed out of fear or worry that I was just beginning to lust. In the end, I was just happy he him and I were finally able to get along.

Fast forward a couple more years, I had lost my living arrangements due to some flooding and needed a place to stay at short notice. My best friend and her boyfriend, Nick, offered to let me stay with them for the time being, and since I was desperate at the time since I had just lost most of my stuff, I agreed. Let's just say that living with them was what lit the fire. At first, it was great. Not many people can say that living with their friends turns out to be successful, as I whole heartedly agree that you really get to know someone once you live with them. Living with them, I quickly realized that I was feeling something for him. The physical attraction was there, clearly. The intellectual attraction was very much so there. It began to be very hard to deal with. Hiding it, for one. The morality of it all, for two. And lastly, the fact that I couldn't tell my best friend, for three. For this reason, and a concoction of other small details, my best friend and I started to get a bit distant -- despite living in the same house. Over time, it just became more difficult to live with it and feeling like I was going behind her back just by having those feelings. It was hard to oppress when I had to see Nick every day.

So I saved some money and moved out. The first couple months I was finally away and living alone, I wasn't speaking with my best friend much. She noticed there was some distance and eventually confronted me about when I would be seeing her again. Eventually, I finally caved and told her everything I was feeling. That I had feelings for Nick and that it would be difficult to be around them both. She told me she had a feeling. She told me she could tell that both of us got along and that we were able to become closer since we started living together, she also confessed to me that she had a feeling Nick would confess to her something similar (though I doubt something like this would happen). We've been at a standstill about it, my best friend doesn't want to cut off the connection, but at the same time, I don't know what else to really do other than walk away? Even if we started hanging out separately without him, he would eventually catch on and want answers.

I fear telling him, to be honest. Just because I want to save myself the embarrassment of confessing feelings to someone who you know won't reciprocate. I've never really been one who was good at doing so. At the same time, a part of me wants to be rejected, so that it's easier to move on. A part of me wants to be selfish and move on from it completely. It's caused me too much pain.