I want to fix this error help! (22M) (18F)

I (22M) have been dating J (18F) for around 7 months now and we’ve had bumps here abd there and we fix and push on. This particular argument is affecting her a lot and im trying to fix it. Let’s begin. This is my first post ever bear with me.

So this Monday I had taken off work because I had an appointment in the early morning. J was drinking at her cousins which i’m fine with I trust her. So she’s asleep as i’m going to my appointment i text her and let her know that im leaving the house and i’ll text when i make it to my destination. I then make it then text her so on do forth till i make it home again. I ended up going to sell my guitar and i texted her to say “im heading out etc.”

So J has a rule/boundary and she doesn’t want me texting or talking to her girl bestfriend “A”. So out of respect I follow, now I arrive at my destination and check my phone and I see A had requested to follow me on IG. Thought it was weird cause I have ignored her request for a while and why is she suddenly trying to follow me again? So I have A’s account restricted. Which allows them to still send messages but won’t let them know I have read them and I can’t answer unless I unrestrict. I look at what the message says “SOS i’m being FR” now i shouldn’t have even answered her because that’s a boundary. Part of me felt like I needed to answer because no one ever says sum like that jokingly. So I answer “What do you need?” A goes “can we call?” I explain i’m busy but just text it to me.

A then proceeds to tell me “J was letting another dude have his hands on her thigh” “She was also being flirty with him” I start freaking out my biggest fear might’ve just come true. After selling my guitar i call her. I have her number because J my gf had me get it from A’s mom but I never used it cause it was a boundary. She explains everything to me and i’m upset. I text J “Yoo lmk when ur up…”. Then end the call and drive home and I park across the street from where she stayed at her cousins. I sit there and then A texts me asking if her wallet is in my car. I say no then we text and discuss and i express how hurt I am. Now me and her bsf are talking abt J and we shittalk. Yeah. I will agree it was extremely dumb of me to shit talk my own gf with her bsf.

Eventually J wakes up and answers me with “??” I ask if she needs a ride and then she ask me “why is your location off?” (I turned my location off when i found out I might’ve been cheated on. I tell her well you’ve had yours off for a bit why can’t i have mine off? She says “K” then i come pick her up. Now i wasn’t supposed to confront her but she kept asking me what the “Yoo lmk when ur up…” was abt and i eventually cracked and said “Why am i hearing from three different ppl that you were letting another guy touch you?” (The three are A her bsf then her older cousin and her younger cousin) She’s goes “are you serious? i’m not doing this i’m walking home.” I say “no sit in the car i’m not gonna let you walk” “Now tell me wth is going on” and then she explains what had happened. “It was my phone he was just sitting next to me nothing happened” I’m still extremely skeptical but i’m also hurt while typing this.

Now I take her word for it now that she’s told me. The fact that three diff ppl said sum similar makes me upset. Now was everyone there drunk? Yes. Then the tides changed to “Why were you talking to A??” (Fml) I explain what i explained earlier in the passage and she’s upset i went out of my way to answer A. Then we bicker back and forth then things wind down.

Hour later I come back to her house and we argue some more and try to resolve this. We start to come to a conclusion when her bsf “A” sends her the text messages from earlier and i hadn’t gotten around to telling J abt them. She gets livid abt the shit talking and now that i reread them it’s not edit talking it’s her bsf. Should i have defend my gf? Yes, but at the time those were sent i was fully convinced i was being cheated on. Now it’s been abt 4 days since and she’s been extremely dry with response and very little reasoning. Her instagram notes say things like “Sugar in your gas tank” and “Feeling cute might burn sum shit later <3” I’m just wondering how do I fix this and regain her trust again?

TLDR: I cross a boundary when gfs bestfriend text me and i answer because it’s abt gf possibly cheating. Confront gf, gf explains situation i believe her. While i was upset i shit talked gf with her bsf. Now gf is upset with me and i wanna fix what i did.