i need help on a confusing situation [21F] [26M]

me [21F] have been with my boyfriend [26M] have been together for a year and 5 months. a few months ago maybe around February i have been having a weird gut feeling. i decided to go on his ipad and i looked through his messages. i ended up finding texts between him and his past girlfriend of 6 years. and it was MONTHS of texting

about 4 months into our relationship my boyfriends dad got deported to mexico and his father ended up calling his past girlfriend cause she could help his father because she had family in mexico. so obviously my boyfriend and her had to keep in contact. my boyfriend ended up going back and fourth to mexico together to figure things out. this situation almost lasted like 9 months and i had no idea i genuinely thought my boyfriend was alone. there was times where my boyfriend went to her house and idk if she went to his. reading those texts i saw a lot of sweet talk and they would buy eachother stuff and they had a lot of deep talks regarding why they didn’t work out. in those messages i say my boyfriend say “i wanted to see where this would go but you don’t communicate which is why we didn’t work out” and then i saw his past girlfriend say “respect your girlfriend and stop cheating on her”. on top of all that my boyfriends birthday was in october, he told me he’s been wanting to go to germany. i told him i couldn’t go cause work and school and i said you can go alone don’t let me stop for from living your life. so her went. with her. they went to germany together apparently they stayed in seperate hotels and did they’re own things but they explored together. (i also forgot to add , in the beginning of our relationship me and my bf used to go to car meets and one time he introduced me as someone else’s name and he told me it was his cousin. and then later i used his ps5 and i saw the same girls name on his ps5 and continued to tell me it was his cousin but that’s when he fessed up and told me it was his past gf)

it’s been 3 months since all of that happened. i decided to stay and i know it’s my responsibility to move on and recently i have. last weekend i saw with him and just communicated how everything has been making me feel and why it’s been making me closed off. he does understand the wrong and he’s sorry and he’s changed his way by blocking her on everything and supporting me and ever since i have felt lighter and i’ve been more loving and everything feel like another honeymoon phase.

my problem rn is that it still haunts me sometimes and i genuinely don’t know how to go on about this. part of it is i feel stupid like i gave this man the benefit of the doubt and i was out here worrying about him praying for him changing for him and putting my all into the relationship while he was lying to me and doing me so wrong. it’s a really deep thing for me. and i don’t hate him or anything it’s just sometimes it hurts me a lot and idk why idk what it is and im tired of everyone telling me he’s a piece of shit and i should leave him cause that’s not what im doing im choosing to stay but im just still hurting yk and i feel terrible telling him this over and over i want to be better for us