PCO - is polycyctic ovaries - it means they have found cysts on the ovaries - but that's not necessarily a problem, as the others have mentioned - lots of people have them...

PCOS - Polycystic ovarian syndrome - it's a collection of symptoms - included the cysts - but often difficulty losing weight (so often women with PCOS are overweight), insulin resistence, excess hair on face a body, irregular/infrequent/heavy periods, acne and difficulty becoming pregnant.... it presents slightly differently for everyone.

You do need to go to your GP and probably a fertility specialist (gynocologist) to check it all out. There may be other things going on for you as well.

Hopefully you can get some advice soon and find out what is going on for you.
I hope it all works out.