OCD claim

I have a 70% PTSD rating. My Doctor and my LCSW therapist both say that I have traits of OCD and they see this a lot with folks with PTSD. They are going to write a nexus if needed. My question is this. 
 

If I submitted a claim for OCD it would be a secondary condition to my rated PTSD so would the VA just combine this with my current PTSD rating or is there a separate rating for OCD. I think my rating would fall under 30 percent based on what I read. It seems to match up with my symptoms. So would they keep my ptsd at 70 then the secondary would list OCD at its own rating of degree example 30?

severak things stem from PTSD. For me it’s OCD and sleep apnea. My doctor has 30 plus years on this subject so I’m getting a nexus that relates my PTSD to aggravation of sleep apnea and I’m going to claim both OCD and a separate claim of secondary to ptsd sleep apnea. I just didn’t know if OCD would be part of the current ptsd rating.