Oh boy, do I understand! I live in a fairly small apartment, 2 bedrooms two baths and 2 small closets. I have had to figure out ways to maximize space since I LOVE clothing (even though it all comes from Thrift Shops!)
I, too, have OCD tendencies. And that is why I got into cleaning houses...putting that to use!
What you need to do is perhaps a bit extreme for you right now. Get a few trash bags. You have to force yourself to go through each room and put in those bags every single thing you dont actually use or wear. Be brutally honest about this! Getting rid of extreme clutter can be very theraputic, as long as you are tough on what you put in those bags.
I do this all the time. For example: I always put new sheets on my bed on Saturdays. IO had bought a nice set of sheets at a thirft shop but over time, they shrank! Tomorrow, I will put those sheets into a trash bag and take them BACK to a thrift shop. I also plan to go through my closet and discard some clothing I truly do not wear.
OCD is common and tricky to work with. What has worked for me is being tough on it all and forcing me to discard stuff. This will help you too and give you a sense of having POWER over the OCD thing.