Question about drinking and consent

I am a 35F in a long term relationship with my bf of 6 years, 37M. I have never thought about cheating on him or leaving him, we are very happy together and I want to spend the rest of my life with him.

This weekend I was out drinking with a group of friends, my bf was aware. I have recently lost about 40 lbs which is relevant for two reasons: 1. I very rarely drink anymore since it is so calorie dense and 2. because of this I get drunk off very little. I remember the early night but quickly things become hazy. One particular guy was there, I will call him Kevin. We are definitely friendly but there has never been anything romantic between us, no flirtation and I am not attracted to him. I remember being in a group with him and some other people, talking to everyone. Then I remember being led some where by him. I don't think I knew where I was going. Then I remember being in a hotel room, I was fully clothed, his pants were down and he was in my mouth. I don't know if he finished. I did not feel like I had sex or even got undressed. I remember feeling like I did not want to be there and that I had to do what he wanted to get it over with and leave. I have no idea if I said no, stop I dont want to. The next memory is me in a cab, going home.

This happened a few days ago and I still have trouble processing. I told my BF the next morning, and I told him that while I was leery to use the word rape I do feel I was too drunk to properly consent. I wish I knew if Kevin preyed on me or if he thought it was a drunken hookup. I go back and forth between feeling like a disgusting slut and feeling like a victim.

I intend to not drink anymore since I was obviously very irresponsible. I also intend to find a therapist. My bf is upset but very supportive, although he is obviously having fallout from this as well. He does believe me. Does anyone have experience with drinking and consent? I don't even know what I am specifically asking here.

tl;dr: When are you too drunk to give consent?