The Mirena delivers about a 5th the amount of circulating hormone, so it might not make you bleed all the time, although bleeding is VERY common for the initial period. How long did you have the implanon in? I have had a MIrena since December 2006 and i would say i bled excessively (started off 21 days a month, gradually reducing to AF for 5-9 days and O spotting for 1-2 days every month) for about a year. For me the waiting was worth it because i've had no problems since and i knew it was the best option for me for a long term contraceptive.

Bx