Polycystic ovaries

I am 23 yrs old and have always had a regular mentrual cycle, however, since the past 4-5 months my cycle has been very irregular. I got my period twice in March and then in April I got it within 14 days! I also have very bad acne. My doc is suspecting that it is polycystic ovaries. Can PCOS also cause periods to come too early? I thought ppl with PCOS dont get their period and that it is usually late.
What tests can confirm the diagnosis of PCOS?
Can one have a normal pelvic ultrasound and still have PCOS?
What about the testosterone level, is that ALWAYS elevated in PCOS? Mine was 2.8, not sure in what units though.
Where and when in the menstrual cycle should the hormonal testing be done? I've read that the testing must be done at a particular point in the cycle, is that correct?
I really want to find out how PCOS can be clinically confirmed, particularily with what tests.

What type of specialists deal with PCOS?

Thanks for your help.

Sarah