I had unprotected sex on Valentine's Day and had unprotected sex again on feburary 22nd while I was on my period. February 22nd was the day my period began. I have short cycles which last only 3 days. I wasn't bleeding much at all and after we had sex my period stopped completely. My urine tests are negative but I been pregnant before where as a ultrasound has to detect my previous child because I was negative in everything. The blood test numbers was positive. Did I miscalculate something? I'm sick just like I was when I was pregnant before. I didn't find out until 3 months I was pregnant with my son