My period last for 3 weeks since i had the iud put in. i just had it taken out and i'm on my period again. why?. how long will it last?

2 different causes: Your irregular bleeding at first was a common side effect of the iud. Your period now is probably more close to when you would have had a period without an iud. Within a month your periods should be back to whatever they are/will be naturally.

Not sure.: You don't specify if you had a paraguard or Mirena (levonorgestrel) iud, and they are quite different. If it was a mirena, (levonorgestrel) which has Progesterone in the iud, it usually causes several months of spotting initially until the uterine lining thins out. If you just had the iud removed it may take several weeks for your own hormones to regulate again. If the bleeding continues check in with your doc.