Linea Nigra-sign of PCOS?

The linea nigra is associated often with hormonal imbalances, but is no more a sign of PCOS than vomiting is of pregnancy. They can happen with one another, but more often than not, the symptoms have other causes. Hormonal birth control can also cause the development of a linea nigra. I have had mine for as long as I can remember, and was diagnosed with PCOS two years ago. Cystic acne is also not necessarily indicative of PCOS but just hormonal imbalances in general, though it is one of the more common symptoms. If you are displaying other symptoms of PCOS, such as more pain than normal during cycles (a little hard to tell if on birth control), fatigue, low energy, hirsutism, male pattern thinning of the hair, coarse body hair, mood changes, or sleep issues, then definitely go talk to a doctor. You don't necessarily need to see a gynecologist, though; typically, a GP is more than capable of making a diagnosis of PCOS. Whoever you're more comfortable with is probably best! If a doctor orders tests, it will likely be a testosterone battery, along with tests for DHEA-S, progesterone, FSH, and LH, though some of those results may not provide an accurate result if you're on the hormonal birth control. They may also order a transvaginal ultrasound for imaging of the ovaries. However, this is not necessary to make a diagnosis of PCOS because abnormal cysts may not be present while you're still presenting clinical signs of PCOS, and thus match enough diagnostic criteria.

Best of luck to you! If you happen to have any questions about PCOS, the diagnostic process, or just wonky ovaries in general, don't be afraid to send me a message. I'm happy to answer anything to the best of my ability. 

Im guessing you are in the US? what tests do they do to diagnose PCOS over there?