Thinking while having sex

There have been many time in my relationship of 8 months where we had amazing sex. I orgasmed and never thought about anyone.

My boyfriend started showing his true colors where he did a lot of fucked up shit , which made me be confused about my feelings because I’m scared that he won’t ever change his bad habits. ( no cheating involved )

I live upstairs from my ex of 2 years, he was my first love and longest love. He broke up with me and I was sad. I never thought about him in the beginning with my current boyfriend, but I started to compare the two of things they have done bad or things my ex wouldn’t have done that my boyfriend does if we were together .

During sex I started thinking a lot. Am I wet enough or is he enjoying it . Now it’s gotten worse where I kinda compare the sex, one thought was “ I had this same feeling with my ex “ or his penis was similar and I would start to think about the sexual feelings I had in total with my ex and my current . ( not thinking of wanting to have sex with my ex , but thinking of the pleasure ) .

Once I thought about the feeling of pleasure so I can orgasm faster. How can I stop this ?