Kate, it's really hard for you and I do sympathise. It is very difficult these days when your friends are having babies. When I was your age, it was accepted as the norm - not every couple could conceive - yes, it was a sadness but after a while we came to terms with it. There is no point in grieving after something which together, you can't do - it was accepted that having a baby is a bonus, not a right, and for some couples it just wasn't going to happen. Forty years on, I'm glad now that I couldn't have children, my lifestyle would be very different, but at the time it was very hard. You are very young IMO, at twenty-five I was still building my career - but there are also other options you could consider at your age, like adoption, if you can't have your own children?
However, you haven't said what treatment you have been having from the doctor or from any infertility clinic - after five years, I imagine that you have been given advice and investigations by your GP? Have you and your partner been tested to see if there is a basic problem, besides your PCOS? The doctor and practice nurse will certainly take you seriously, and you need to see them anyway to see if they will refer you to someone, to talk through your feelings and help you manage the way you feel. If you slide into a depressive state of mind, that won't help, but you can be helped with that - but you need to ask for the help and I know myself how difficult that is.
You posted some hours ago so I hope you see this and get some other good postive replies, to help you. Good luck - keep posting on here, it does help.