Heavy cramps and clear liquid coming out of me

Sa
Friends, I'm wondering if any of you have had this. I'm on cycle day 24, approximately 6 days before I should start my period and today I've suddenly had INTENSE cramps. But the cramps are more in my cervix, not in my uterus. 
So, I thought, okay I guess my period is coming early. I went to the bathroom and there was a little blood on the toilet paper, not enough to stain my underwear. Then an hour later, a big gush of watery fluid (enough to soak my underwear and into my pants) came out, I went to the bathroom and wipes and it was slightly blood stained, but mostly just water. Since then I'm continuing to leak clear fluid, but not as dramatic of gushes.
I did get an IUD put in a few months ago, this hasn't happened before but I'm wondering if it could be from the IUD? Anyone have this happen before? Could this be a sign of an STI? I have been with one new partner since getting tested for STIs 2 months ago, but he says he's clean (of course I do need to be tested again soon).
Please help, I'm feeling frustrated and a little nervous.