This is a wild ride so buckle in.

(i am not using real names in this)

A bit of background info

i started at a new school this year, and i didn't know anyone. After a month or so i was adopted by a friend group, the friend group consists of the people i would normally be with (gay kids and the outcasts) When i joined this group i met a girl, we'll call her Amy. After about a week or so of being friends she told me that she had a crush on me and asked me if i could be her girlfriend or go on a date with her, i accepted mainly because i felt bad (i am a very sensitive person and i am manipulated easily). Amy and i dated for a week, and i hated the entire relationship because i just didn't love her. At the same time i was dating her, i was starting to develop feelings for a guy in the group that i had become good friends with and had a lot in common with me (we'll call him sean). I broke up with Amy after a week into our relationship because i felt guilty and was just unhappy. a couple weeks later i went over to sean's house to hangout (we both like to skate, so he invited me over to skate his neighborhood) while i was there he was acting very shy. In school i found out from one of our friends that he actually had a crush on me, i called him after school i confessed my feelings to him. Him and I have been together for 8 months and we are really happy together. Amy, has tried multiple times to ruin our relationship and even tried to kiss me when we were having a group meetup. Another remember in our group, Rose, is like the therapist friend, she knows basically everything about everyone in our group, and she told me that amy keeps going back and forth between being obsessed with me and hating me.

Now what i need help with:

Amy recently told me that rose likes sean, and this made me extremely nervous because i have been cheated on before in this same type of situation. Rose and sean have been best friends for a while. Rose also identifies as Aroace (no romantic or sexual attraction). I know it's dumb, but i can't help but be scared. I have noticed rose physically getting really close to sean (like getting her face close to his, touching his knee, etc.) as well as getting in between us (she once pushed me away from sean when him and i were sitting next to each other to take my spot). I know i'm probably just insecure and overthinking it, but i can't help it. i can't stop feeling this way. I trust sean, but im still nervous. i have actually grown to not like rose, and i feel guilty because of it.

Please give me advice on how to get over this ;-;