Quite possible but. Not the only thing. Please get seen by your doctor.
How common is is pcos? I feel like I have all the symptoms (irregular/missed periods, weight gain, excess hair on lower belly and neck, thin hair)
Very common. Pcos is very common. It is one of the most common conditions obgyns treat. Weight loss is key. Birth control pills can help regulate cycles. When you go for a visit ask to have your thyroid checked as well.
Possibly. Extreme ranges in weight...very heavy or very thin can both throw off your cycle. However, there are other causes so if this is a persistent problem or if you go more than 8 weeks form last period, call gyn. For more info www. Askyourgynecologist. Org.
Missed Period for months, chin acne, hair growth, and weight gain. (No PCO and normal hormonal levels)?
Abnormal. I would see an endocrinologist for a follow up to monitor hormones something sound wrong.
Many symptoms. Start by going as soon as possible to a gynecologist. Most things can be taken care of there but if not a referral will be advised.