Likelihood of being pregnant

After getting my IUD removed in April because it started to grow into my uterus, I have not had a period. My fiancé and I have been having unprotected sex the entire time since then. I went to the doctors on the 5/28 and they did the blood test, and ultrasounds to see why I wasn’t having a period and if I was pregnant. The tests showed nothing, and I wasn’t pregnant. Yesterday, I had bright red, watery blood started but very very light and it only lasted for about 3 hours. I have not bleed since. What is the likelihood of it being implantation bleeding? I’m really hoping for a baby, but do not want to get my hopes up.