First month of Copper IUD

So I had my copper IUD put in March 17, I had unprotected sex 3 days before and 2 days after. I was told it could be used as emergency contraception and read copper IUDs start working immediately.

My period was supposed to come 2 days ago (March 26th). I had cramps but no blood flow. Is it common for you're period to be a little weird the first few months?

I took a first response pregnancy test that came back negative yesterday. But I'm still weirded out that my period is late. Hopefully I'm just being paranoid. Thoughts?

Also I got a stomach bug last night (vomiting and diarreah) I don't know if that's important.

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