I feel so disloyal to my boyfriend

i feel like such a whore. i love my boyfriend to death but my thoughts are plagued with my ex, i keep thinking about the memories we made, good and bad and i feel so terrible i feel disgusting to the point where i wanna cry. My boyfriend is my whole world but sometimes i feel like i’m convincing myself that, I don’t know what to do, i wanna text my ex, not even to be flirty but just to see how he’s doing I still want him in my life but i know i shouldn’t. my boyfriend is genuinely one of the best people i know, he’s so sweet to me we do everything together and i trust him with my whole heart i feel like i can tell him everything, but i know i can’t tell him this so that’s why i feel so disloyal. i hate myself so much for this i even gave in one time and texted him which almost ended our relationship. god i don’t know what to do i just want this feeling gone i don’t wanna think about him, i hate him for what he did to me so why do i keep thinking about him. (i’m sorry if some of this doesn’t make sense and spelling mistakes it’s late)