I definitely flip flop back and forth from the way you're feeling... , There are plenty of times that I question my relationship i'm a lot younger than my partner and do get scared that i'm making a mistake by choosing to get married so young however my situation has me in absolute tears because I don't want to leave my partner but feel guilty that I should because I think this way and feel even more guilty if in those moments when i'm being myself and not filled with the anxiety I give him affection and then it triggers my mind to say "You're being fake " ...

Sometimes I get the ROCD where I become obsessed that he doesn't actually love me or I'll do something that will sabotage the relationship (lie , cheat etc...) However I always have this thing in me that I believe is my logical unharmed part of my brain that always brings me back to this state of bliss and absolute love for my partner when you come down from this anxiety of "are we meant to be or not" do you return to that state of love for your partner ? does everything seem to feel normal and comfortable ? Because if so i'm more than positive it's just your OCD acting up . but since i'm no professional and a current sufferer myself, if you want your relationship to work I would look into a relationship therapist someone who can delve deeper into the issue from a professional standpoint and lay all your history on the line I would look into soon as well.

Much Luck to you