What Does Positive Pregnancy Test Followed By Spotting Indicate?

Hello, I had three faint positive lines on pregnancy tests last Thursday, Friday and Saturday. I got a blood test Friday and my hgc levels were 11. I estimate I m four weeks pregnant. I have another blood test tomorrow to check the levels but I have been spotting for five days and the urine tests are now coming out negitive. Is it possible that I m still pregnant?