New medicine, new worries

So I’m almost at the end of the process of switching over from one medication to another and I’m noticing old habits from years ago and old thought loops from years ago are coming back, but I don’t understand why. Yes, they make me feel uncomfortable, but I also know that I’m fine now, i’ve been doing ERP and facing my fears, so these thoughts shouldn’t happen should they? And when they keep coming up, they make my more emotional side feel scared, but it doesn’t completely take me over like at once instead letting my rational side and keeping myself calm as a cucumber. I make it frustrating initially, but instead of scolding myself and beating myself up for having these thoughts, I just acknowledge what I’m feeling and try to find the reason as to why they’re popping up, because my OCD does get more active during stressful situations, I basically see it as my 21 year-old self comforting my high school self who still feels scared/traumatized by what triggered my OCD in the first place. I just want to know that if people switching from one medication to the other experience older symptoms popping back up. I’m switching from Extalopram to Fluvoxamine BTW (I know I misspelled those in some form.)