I know that Mirena helps with alot of complications due to endometriosis, but if you feel that it is causing you to have suicidal thoughts, PLEASE see your doctor imediately!! Mirena is known to cause depression/mood swings in its users, and if yours is that bad then you need to seek help right away. If you choose to stay on Mirena then you will at least need to discuss further treatment options for Depression with your doctor. Please seek help!
Also, you should for no reason be able to feel your IUD inside you. If you feel that it is poking you then it might have shifted out of place, so make sure you tell your doctor that!