My anti-ccp is >300, and I have been on RA meds but still in great pain for 7 years. Is it possible that anything else could cause that test result?

Very unlikely. Ask your treating physician what your CRP is and is it elevated. If it is, your inflammation remains out of control. Rheumatoid factors can fall with dmard type-drugs, but they have no effect on ccp antibody levels. But I have never seen anyone with that high a titer who did not have ra!
Yes but less likely. Anti ccp is fairly specific for ra. Other conditions such as psoriatic arthritis, lupus, and hepatitis c can also cause elevations in anti ccp. Perhaps you need to be on other medicines for this condition. Unsure if you have been a candidate for Remicade (infliximab) or enbrel?