What Causes Abnormal Vaginal Bleeding While On Nova T Coil?

I got a Nova T copper (non-hormonal) coil fitted a couple of weeks ago and was bleeding for a week after it was fitted and then this stopped however when my hubby and I had sex, I started bleeding again and I still am to this day. I am not feeling crampy or anything like that, I am completely comfortable with my coil but starting to get slightly agitated as I came off my mini-pill as it caused me to bleed constantly and I stuck with that for 3 months so for the past 4 months I can count on both hands how many days I have not been bleeding.