Akmi, I was in your exact situation and have had the Mirena for a bit over a year. I have found it to be pretty good. I spotted for about 6 weeks when it was inserted, but since then I haven't had any problems. AF is a lot lighter, and a little irregular.

I recommend you at least try it. It's a pretty good option for bfing mums who have limited choices and while it's not for everyone, it is easily removed and not very expensive so you don't really have much to lose. GL.