My ob tested me for yeast in. and other things for a rash that looks like ringworm but it all came back neg. now she want me to see an infectiousdease?

Appropriate: That would be appropriate - a biopsy would also be appropriate assuming cultures for bacteria are negative. Some doctors would try topical steroids - unless the symptoms are quite severe and warrant an immediate consult.

Another option: In addition to seeing an infectious disease specialist, another option may be to see a dermatologist who may also be able to help diagnose your condition.