Not sure if I have a cyst

So let me start off by saying that I have a very regular cycle so I don't think I have PCOS. Last month after my fertile window I got this super sharp pain which I thought might be implantation. I had to sit down it came on so suddenly. Anyway I wasn't pregnant so looking back I'm thinking it may have been a cyst. tomorrow starts my fertile window and I'm having dull one sided pain. I'm worried I might have a cyst. I read that it's not a big deal because they serve a function but I'm still worried.