I just need to rant

Hey guys so a couple days ago my boyfriend and I were ft and we got into a mini fight not a big deal at all. Then we hung up bc I got upset. He was texting me he sent me a vid where he was logging into a app and I saw his password. I KNOW I SHOULDN'T HAVE DONE THIS but I always had doubts bc I was cheated on before and he lives far away. I logged into his Instagram and saw messages from him to other girls. I was very upset. He was sending hearts to girls and telling a girl he'll smash her and he thought she was cute but he had a girl but "you know what I'm trying to say" I was very angry (I have some anger issues) I sent him the ss and I was so upset and was cursing him out which I shouldn't have done but I was upset. I also found a message after I requested for his snap password I also gave him mine bc I have nothing to hide. I found a message to his bsf where he was asking him if he should stay with me or break up with me for his exs friend so he could get back at her. He also said to her "I would love to go out with but" and she replied " only to get back at his ex" but then recently he was texting everyone about me and how much he loves me. I'm just worried bc he's close to this girl and I dont want him to leave me for her. I love him but can't trust him he said to give me some times to show me that he's a good guys and it was a stupid mistake. I'm hurt now but I'm giving it a last chance. Please just advise me how to feel better in away and don't day anything nasty. I also felt like not enough or not good for him. Am I being stupid for feeling this way?💕💕