Pregnancy scare? What are the chances for someone like me? Plan b concerns…

Yeah I may or may not have fucked up. I’ve since been off of the birth control patch for abt 3? months maybe longer as it was making me really sick and depressed. (Nothing against BC I’m just someone who is more prone to these symptoms) I’ve since felt better but yesterday I had unprotected sex with my partner and I fear a drop of semen could’ve gotten in me. However…I’ve had other pregnancy scares in the past and ended up not pregnant maybe when I should’ve been. I don’t get my period at all, I had it once or twice at 13 and never again naturally, I took BC at 16 for a few months but got incredibly sick and stopped. I do not get my period at all. I’m in my mid 20s now and I still don’t, I have a rather low libido too. I was diagnosed with PCOS at 16 but the cysts disappeared and havent reappeared since I was 20. Despite that still no period and possibly other issues that I may never know about as my doctors kinda just shrug it off especially since I’m not someone who plans to have children any time soon. Ovulation? Yeah not sure if I know her. Tracking my cycle is difficult because well it feels like i don’t even have one! My bf got me a plan b just in case to ease my fears but I’m scared to take it. I know I know it’s best to get sick for a bit than be pregnant but when I tell you I get sick from this kinda thing I get SICK. I’m being a wuss abt it yeah and I may be coping my way out of it but seriously what are the chances of someone like me getting pregnant when I’m seemingly unable to? Anybody similar to me out there? who has maybe also taken plan b to ease my worries?