Pregnancy possibility

So I had an IUD for a whole year and then this month it fell out. Like I went to the dr for pain and he said the iud was out of my uterus and just laying in my vagina. There was no way to tell how long it had been like that so we aren't sure how long I was unprotected. That was on a Tuesday and I stared a pill that Sunday but only took it for two days. Ovulation was a week and a half later and sex happend a few times. I've had some symptoms that could be either high estrogen, pms , or pregnancy. How soon can a blood test detect positive pregnancy? I am high risk due to so many prior losses and need to know ASAP if I am. Can anyone relate or help me?