Am 19 year old guy i have a girlfriend dating we have been dating for a few months now and I’ve been hurt i really love her alot, advice me?

I’ve been stupid enough to believe all her lies even after knowing the truth recently after a long time when she couldn’t lie more and was stuck she admitted to her lies i gave her another chance she is my first girlfriend she has dated another guy for over a year she also used to flirt alot i don’t have friends as such and she has too many friends she has too many guy friends it makes me very insecure as she has already broken my trust so many times by hiding and lying i never do anything that would hurt her i am truthful and loyal to her and i try to see that she is always happy but i need help with how to adjust because I’ve never had many friends and a group or close friends that were girls so i don’t understand all that and her friendships with so many guys makes me very insecure besides i feel very useless i have no talent am not good at anything i feel very sad i am good for nothing and she is very smart am happy for her. I can’t shout or argue with her but she shows me a lot of attitude if i try to tell her am hurt and if i tell her what she has done wrong she starts getting irritated says she docent have time for all this and makes me feel i did something wrong by talking to her she dosnt like it if you tell her what wrong she has done and then i end up saying sorry to her she is very busy with her studies she wudnt like it and i don’t want to pressurise her. I wanted to know what i can do to feel happy and how i can be productive i dont want to feel depressed help