I have had problems all my life too but it's become really noticeable in the last few years.
For around 3 years I was taking a contracepotive pill called Cerezette, which works by tricking your body into thinking you're pregnant - therefore you don't release eggs and as a result don't have a period. Sounds scary but it's safe (apparently). Due to my ever increasing weight and struggle with loosing it, I asked my doc back in January/February this year if I could change incase that it what was making me struggle more than ever with my weight.
I changed to a pill called Yasmin, which you are supposed to have periods on. 6 months after stopping Cerezette I still was yet to have a period - which is when I went back to the docs. She said she thought I had PCOS and sent me for blood tests and scans.
I had an internal scan (they put a probe thing inside of me).
I also have random hairs on my chin and around my belly button, which my b/f kindly plucks out for me.
They do say that irregular periods (or non existent) are a big sign of PCOS.
After loosing my first stone I got my first period in over 3 years.