If the coil is in place, you would know by checking the threads through the vagina. If you can find them by palpating with your fingers, it means that the IUD is in place. Spotting after intercourse could be due to an unhealthy cervix
with some cervicitis
or an erosion, vaginitis
, a polyp of the cervix or endometrium or some hormone imbalance
. A local exam should be done to clarify. To know what is causing all these symptoms, you should get a trans-vaginal sonogram and if needed, a pelvic MRI
to know the location of the coil. Hope this helps.