The Mirena Coil- bleeding and pain agter sex

So I had the coil fitted back in the end of April this year, to help with my periods associated with PCOS and Endometriosis, and it was incredibly painful when fitted and had bad pains for a few months after! I had sex about 2 months ago and bled a lot, both myself and him were covered. Then another time there was a little blood then it was fine for a month or so. I then had sex again a few days ago with someone new and am bleeding again. Is this normal? There is still some pain associated with it but the doctors just brush it off and say it will be fine. But I’m not convinced that this should be happening. Has anyone else experienced this?