A positive ANA is only one of the 11 criteria that a lupus diagnosis is based on. Go to www.lupus.org
for complete information. It IS possible to have lupus with a negative ANA. I think a second opinion is called for if your rheumatologist has decided in spite of all of your other symptoms, that the negative ANA completely rules out Lupus, and/or isn't looking for another possible AI condition.
Something is going on with you and it's important to pursue a diagnosis and treatment, regardless of what the condition turns out to be.
Good luck to you!