Pregnant on iud?

Hello, So for the last couple days I been cramping on & off. My period was suppose to come last week (the 24th) I have been gaining a little weight & a couple days ago i start having to use the bathroom more frequently. Today I did experience a little, little spotting but No period yet just discharge. Could I be pregnant or my body is just changing more. I have taking a couple pregnancy tests but came out negative. But then again it will be to early to show I’m pregnant (through a dollar store). I’m on the Paragard IUD ( for about 1yr & a half). The day before I had unprotected sex I couldn’t find my IUD strings but I figured it was still in place and I found out I was ovulating that day (also hurt doing sex) A few days later the strings appeared (does feel like it’s a little bit further in).

I’m already a mother of two boys.