Help 😩 I’m a bad girlfriend

So my boyfriend is so sweet we have 3 years dating... but we broke up a couple times... last year around this time I broke up with him because I felt like things wasn’t working out and wasn’t how they use to... I felt like he was trying to change me because I love wearing high waisted jeans and crop tops but he wouldn’t let me cuz he says I have a big but which I feel I don’t... etc but while we was broken up he tried to get me back and He showed me the engagement ring (which I didn’t know he had) it was beautiful... I’m 18 now which I feel I have grown from the immature of hurting him because while we was broken up I had kissed a guy at a after party while I was on vacation in Texas ... I felt terrible and I told him months later... he was hurt but still stayed with me (that happened when I was 16)... then when I was 17 I broke up with him while I was in Mexico because he got mad that I wore high waisted jeans and a white crop top, I told him I wore it to the funeral of the baby boy that died since we had to wear white that’s all I had... so I broke up with him and i ended up sleeping with my ex boyfriend... which was a complete mistake and I regret... my boyfriend knows that I slept with someone else and it’s hard for him to move on from it ...

How can I make him happy and make him feel like I appreciate him... he says he trust me but he can’t forget about the past and he is very hurt how can I make him feel sure that he wants a life with me?