I have really bad insecurities about other girls around my bf

I am in a committed relationship with my bf of almost two years. He mainly just connects/gets along with females more than guys. While I'm the complete opposite, I have more guy friends than girl friends. My insecurities stems from years of betrayal of my girl friends most of them ended up with my boyfriends. So I have serious trust issues. My boyfriend is very close with his ex girlfriend. His ex girlfriend might show up for his graduation and I bought it to him which ended up in argument. I know my behavior is toxic and negative. I know I have to change that but I dont know how. I know this jealousy feeling is more me being scared of being left for someone else.