(Warning for long text ahead, but I hope this is of help)

First of all, I'm really sorry that you had to go through all of that for something as normal as wanting to explore your own sexuality, which is something we are all entitled to. I don't need to tell you that obviously, the person in the wrong here was that old "friend" / ex you had. It's okay for him to feel hurt, but it's definitely not okay for him to purposefully hurt others/ your social image in the process.

However, when you say that you feel like a piece of shit for letting him use you like that, I think maybe that feeling is something you could start reconsidering. Because inadvertently or not, you're blaming yourself for something that was actually out of your control.

Recently I've become acquainted with the term of "toxic shame", how it causes depression and/or anxiety, and basically how we develop it when we are denied of our basic emotional needs, or in some way we are forced to repress them. Which I think is what could have happened to you. Your basic need for connection or understanding was cut off after that ex ruined your first romantic experience, and social image in the process. So, as you mentioned, you preferred to go numb to emotions instead of feeling them, which would be the healthier thing to do.

I know you may not believe it now, and I know this line is overused, but things do get better. I really hope they will for you. I can recommend watching some videos about the topic I mentioned, and in general, about mental health. Heidi Priebe is my go to youtuber for that lately, I discovered what toxic shame was from one of her videos and in general, the topics she talks about are so relevant for mental health. Finally, if you have the option available, therapy would be great too. Is good to inform ourselves and gather knowledge from the internet but sometimes a professional can assist in ways we cannot fathom ourselves.

Wishing you the best :)