P.S. And yes I have PCOS and had cramping all the time and it was usually on one side predominantly over the other. Turns out my left ovary was swollen and cystic. These cysts are not cancerous; they are caused by hormonal imbalance. There are medications you can take to get it under control. If you're overweight then losing weight can drastically improve the symptoms and it can even go away.
Another issue with PCOS is insulin resistance. PCOS can cause you to not ovulate but you can still get a period with the syndrome.
You could have a cyst or have a condition called Polycystic Ovarian Syndrome which can cause cramping throughout your cycle, whether you're close to your period or not. You can get blood tests done to check hormone levels (as PCOS occurs due to hormonal imbalance) and get a sonogram to check out your ovaries.