I am in so much pain right now.

I’m feeling pain both in my uterus and I’m feeling rectal pain as well. I checked my strings, they’re unusually low. (I felt them while inserting half a finger.) And I know the cervix is supposed to sit weird during your period, which it’s day three of. But I’m still worried. I feel very nauseous. I’m too afraid to put in another tampon for fear of tugging my strings. Which is hard because I have very heaving periods with my IUD, and pads won’t cut it. Help?