Many thanks for your question.
The bleeding pattern with the copper coil is usually a regular period but a little longer and heavier than your normal period. The bleeding pattern with the hormone coil is usually a lot of irregular bleeding in the first six months which then improves and most people have no bleeding or infrequent bleeding.
If you have had bleeding on the mini pill for 2 years then most clinicians will want to do a thorough investigation before fitting the coil. The bleeding that you are having on the pill might be due to the pill but they will also want to do a check for sexually transmitted infection, make sure that you are up to date with your smear tests and possibly do an ultrasound scan to look at the lining of your womb. Those tests are just part of the process to ensure that the bleeding is due to the pill and that there are no other treatable causes.
Combined hormonal methods such as the combined pill, patch or vaginal ring are generally good for period control, so it might also be worth considering these.