The doctor says I have PCOS but I don't believe it?

I took the morning after pill in april 28 and then had spotting for a week. The next month (May) there was no period only spotting. In june I finally got my period on the 19th. I made an appointment with a Nurse Practitioner just to make sure everything was okay and got an ultrasound. I was told I have PCOS however I have no excess hair, no blading, no acne, no excess weight gain, and I have never missed a period except for the month of may (which I think was because of the Plan B pill). When I do get my period it last 4 days. Also in January of that same year I had an ultrasound by an OBGYN who said I had small follicles in my ovaries which was normal he said, but overall I was fine. So how could I go from be fine to having PCOS in five months?? I am only 22 and I have not tired to have children and neither do I have any problems with my blood sugar. Should I get a second opinion?