My right nipple occasionally turns white and is really painful, could it be raynaud's?

Maybe; Dr. can check. Raynaud's disease is due to spasm of blood vessels supplying the fingers and toes, and sometimes other parts of the body. Symptoms are often symmetrical. People vary in the symptoms they get with any disorder, so it is possible that one could have symptoms in just one body part . There may be a malformation in the artery going to that area. A primary care or rheumatology doctor can evaluate.
Yes. Raynaud's affecting the nipples is described in the literature. The white discoloration is the first and most important finding, typically followed by blue and red changes.