I (20F) have to choose between my boyfriend (24M) and my best friend (22M)

Hello all. I hope you’re doing well. I’ll be calling my boyfriend BF and my best friend BSF. This is my first boyfriend, and I don’t have much relationship experience. Please be understanding and kind.

I met a guy online. Things were wonderful for about a month or two (It’s been about five months now), but then he admitted that he was obsessed with me. He wanted to talk constantly, on the phone for 2 or 3 days at a time, asking me to share my address, get an app so he could track me, breaking down when I wasn’t there, and more. If I suggested we take things slowly, he would jokingly threaten to harm himself or other people. He’s told everyone he knows, friends and family alike, that we’ll be getting married, and he’s even had me talk to his parents. One day he started calling me his girlfriend without asking me out. It’s confusing; most of the time he’s very sweet, funny, texts me romantic things, and is generally a great guy who I wouldn’t mind being with.

BSF has been with me for about five years. He’s my only other friend and has given me great advice the entire time we’ve known one another. BSF has always hated BF, and vice versa. They constantly encourage me to stop talking to the other. I have always had a hard time knowing when and how to leave something behind. I’m mentally disabled and disordered, and that impacts my ability to process things, which BSF has helped me with. For most of my life, I’ve been a shut-in and had people make every decision for me, usually not by choice. It’s left me feeling uncertain in my own judgment and, admittedly, compliant with whatever decisions are made for me. I hate when BSF takes that responsibility, both because that shouldn’t be his job and because I need to learn to make my own decisions.

BSF and I had our first-ever “fight” over this relationship because he felt I was being inconsiderate regarding why he was concerned about BF and I, and we stopped talking for almost a week before apologizing, as I stopped talking to BF for him. But after a few days, I started feeling this gnawing sense of guilt and physical sickness at the thought of no longer being with BF. I’m not sure if it’s love. I’m happy at the thought of us being together, but then it’s ruined by the thought of losing BSF. I’ve been miserable, and fighting the urge to check my messages and return to BF because BSF said the whole ordeal was worrying him.

I don’t want to listen to what either of them are saying I should do, and I don’t have anybody else to ask. I don’t want to lose either of them, but they’re both saying the other is unhealthy, claiming the other is too controlling. Every time I try to think of what I want, it’s a jumbled mess of anxiety, and their opinions still influence me. Is there some way to know if you’re in love with someone? And how would you go about leaving someone who's unstable? If it’s unhealthy, how do you ignore the compulsion to stay or get them help? Could I possibly explain to BSF that I just want to see where this goes instead of letting him choose for me? I’m at a complete loss.