I took a pregnancy test and came out positive, but the ultrasound does not show any implantation. What do I do?

Please insist on blood test for HCG. I had similar case. I was positive I was pregnant, 6 test kits, all clearly positive. But when I went to the gynae's, there was no heartbeat and doctor couldn't see anything. He took my bloodtest for HCG and arranged for another the next week. By right, if I am pregnant, my HCG levels would have increase. 2 days before the next blood test, I felt a sharp pain in my stomach. I thought I could sleep it off but I ended up calling everyone to come back home and safe me. Long story short, I had etopic and lost 2.5l of blood internally. The surgeon told me the next day that if I had insisted on ignoring the pain or if I had got in surgery any later, I could have basically bled to death.