<human>: This is gonna be a long one , but I've never had an issue I couldn't sort out myself yet I'm over my head here...

My gf (24f) moved to a new city this year and had a hard time adjust with all her friends being back in the city I was living In. We been together for three years.

She loves her program now and has made a great friend.... 

So little about me: I use to be extremely jealous, my first gf cheated on me multiple times and since it has shaped how I function in relationships. Since then I have tried to learn to be rational and calm. 

back to the issue:
Her new friend likes her. He has bought her love gifts, asked her out, sleep over and flirts with her.

I understand, my girlfriend is beautiful and sexy and cute. Ive tried to accept that they are friends and its a one sided relationship in terms of who likes who. She constantly tells me she doesn't like him its just him that likes her but she ALWAYS talks about him and what he's doing and what he thinks (its not always positive but whenever I'm with her she's glued to her cell)

Today I drove down for a visit to support her in her sporting event. She went to drop off her keys so he could housesit her pet. Not knowing my way around the city I was suppose to follow her so not to get lost. She told me I wasn't allowed too because he would be upset and last time I came down he avoided her and his friends because I was there... Why the fuck does he get to be mad he's the one hitting on my girlfriend and all I done is trying to be accepting of their friendship. 

How do I handle this? I'm pissed and upset and I feel like I could be losing her to him... help :-(

I did this from my phone if u need anything clarified just ask

Summarize the given text in a few sentences.
<bot>: help.  I (22m) feel my girlfriend (24f) is phasing me out for another guy (19m) after 3 years together. I was