Your symptoms are some that are common in PCOS, but also can occur without it. To be honest, your symptoms sound like mine as I have battled with acne for years (Im 28), I have to work really hard just to maintain my weight and stay a size 12, and very irregular periods. I dont believe I have PCOS although have never been tested.
Your doctor can provide advice and arrange testing to diagnose or disprove PCOS (this will involve blood tests, maybe an ultrasound scan of pelvic organs).
There are a number of things that can be done if PCOS is diagnosed, such as anti-androgen medication (many PCOS sufferers have high levels of testosterone, the male sex hormone). This can help with acne and hirsutism (excessive facial hair growth).
Other treatments include diabetic medication as PCOS is closely linked to insulin resistance.
Most other treatments will include lifestyle changes such as changing to a low GI diet and regular exercise which should reduce obesity.
Make an appointment with your GP (go for a female if possible, generally more sympathetic with this kind of thing and you may feel more comfortable discussing symptoms as they will ask about your menstrual cycle, facial hair growth etc) and get the ball rolling with regards to some tests. And at least if you find out you don't have PCOS (fingers crossed!) you will be able to get some help with your other symptoms, most probably an oral contraceptive to regulate your hormones.