When can I get a "real" positive after loss?

Ok, so I lost my son Abel at 15 weeks. The D&C was on September 1st. My first period was on September 11th. My next period is due day after tomorrow (October 9th). I took a test about a week after Abel died and it was faint positive still. I took a test last week and it was soooo faint that I'm not even sure that it was a there at all or if my eyes were tricking me. This is what I got today. It's faint but clearly there. I'm cramping a little though. Anyways, how will I know if it's real or just left over from the baby I lost?? I don't want to look like an idiot calling the doctor for a false positive.