It is really nobody's business but your own if you are or are not trans. Please, do not rely on any therapist, doctor, family member or member of Susan's forum to make that decision for you.
If you are, you should know sooner or later.
As for OCD, I have never heard if it being a cause for trans feelings. I have heard of trans folk with OCD. I have heard transition has helped their OCD in some cases. I will not pretend to back that up with science since I have none.
The MAYO Clinic is famous, but I wouldn't trust their best pediotrist to operate on my brain. If they don't know trans, they lack experience. They may be fine. They may not. Treating trans patients is not brain surgery.
Every single trans person who transitions that I can think of, has obsessed over being trans. It does not mean we all share your OCD. What it means is obsession is part of it. OCD may amplify that obsession, I can see that as a possibility... just like gender dysphoria can amplify depression.
If you are adult or nearing adulthood, you should start considering taking a large role in selecting your own medical care.