I am 17 years old and have been with my boyfriend for a year. We got together when he left his girlfriend for me. Back then I told him that I was not happy for him to be messaging/hanging out with other girls which he had done previously and he accepted it.
Earlier this year I had to stay off school for two months due to illness and when I came back he had formed a friendship group full of girls he had previously fancied. I ignored it at first and tried to accept it, but recently it's been getting worse where on a daily basis he is messaging/hanging out/flirting with other girls. I brought it up with him and told him I felt disrespected and that regardless of whether he feels it is flirting or not, it makes me uncomfortable. Often when I complain about things he does he becomes incredibly defensive and turns the table on me, accusing me of controlling him and stripping him from his social life.
I am sick of my boyfriend flirting with other girls in front of me but whenever I try to talk about it it turns into a fight and we just go round in circles. What do I do? Do I give him an ultimatum? Am I over exaggerating and controlling him? If so, how do I feel more secure?