IUD bleeding?

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I have copper iud for about a year now 
Always been good just heavy first 2 day period like normal but I had my period 1 week ago and yesterday I had some light bleeding. Came to think it's was because my husband and I had made love twice  with in the same hour. But today I start to bleed again light bleeding almost watery but now it's get thicker still very very light 
So I'm wondering what it can be or is it normal? Any suggestions or ideas 💡