Is this normal?

I've been very confused for a long time..

to make a long story short, im an F20 in a 3 years long relationship. we've tried an open relationship from time to time, i like the thought, but when doing it, i hate every part.

here comes my confusion. all my life, I've never been able to fantasize about sex with a person i know. It feels wrong. i fantasize a lot, but it's always someone fictional.. and I actually don't really feel the drive to have sex with real people.

real people are scary and unpredictable, and sex is ALWAYS better in my imagination. I get uncomfortable when people flirt with me (other than my boyfriend, whom I also enjoy having sex with. I have a low dex drive, tho).. when my friends talk about having fun flirting with someone, ect i get so jealous, i want to enjoy it, but i dont, and it makes me feel so broken compared to others my age, like im lacking a very important part of being young and having fun.

how can I like the thought of being free, being in an open relationship, and having sex and flirting, but I dont like doing it irl and find it uncomfortable..

I have cptsd and maybe schizophrenia.. I dont know if that could explain it.. I'm so lost. Does anyone have any tips? I've been spiraling for a year with this now.