My girlfriend just told me to look on the bright side while I’m having an episode and I feel like I’m being misunderstood

Have you tried to sit down with her and try to explain to her what it’s like to have OCD and how you can’t really “just look on the bright side”? Sitting down and explaining it may help her understand that, while unfortunate, our way of thinking is altered and that OCD makes it so it’s hard to listen to the positive sometimes. 

sometimes ocd is super hard to understand, try to explain how she could help

Sometimes others people's pain causes this notebook type response in people, they so badly want to make you feel better they hand you positivity, and while good intent,it can feel invalidating. Forgive and let tomorrow be a new day.

If you want to, when you're in a calm good mindset you can talk about how you'd prefer to be approached during an episode. 