Same boat as you. PCOS, copper coil and I take Metformin.
I've had three different copper coils now. First was a 10 year that was removed after 18 months because it wasn't settling as the Dr thought it was too big as I'd not had a child.
The second was a five year one that was removed after 4.5 years when I wanted to try for a baby.
The third one I've currently got is a 10 year that was inserted 6 weeks to the day after my c-section.
The first insertion was horrible. My cervix went into shock and I hadn't prepared with any kind of pain killers. I'd gone on the bus and had no one with me so it was an absolute trauma getting home. I ended up in the loo at the health centre with chronic diarrhoea from the pain.
Second and third ones I made sure I took the good drugs (cocodomol plus some ibuprofen) about an hour before I went and all I felt was a slight pinch. I also had my now DH with me for those two.
The first coil my periods were super heavy for the duration. The first month I flooded badly and I was at a hen do weekend hundreds of miles from home. It was awful. The pain was shocking too. This was due to it not fitting well. Periods eventually became painless but I still flooded each month until it was taken out.
Second one the first period was heavier than usual and incredibly painful. I think it took a couple of months for the pain to gradually disappear and the periods settled down too normal levels.
Third one I've literally felt and seen no difference in either pain or flow! I think this is because I've now had a child and my womb is no longer fresh out the box.
I recommend it, despite my experiences. I can't have hormones because 1) I'm overweight and can only have the mini pill and 2) the mini pill/injection, etc send me bat shit crazy and turn me into a raving psycho