what is considered spotting?

So I have taken four test that all came back positive. Then yesterday at work I started to bleeding mildly and it's still lingering around not enough for a pad or tampon just enough when I wipe sometimes it darker and other time it's light. It been slow but still there for about 24 hours. My period is three weeks late and never off track, so I know it's real. But now I am worried that it's a chemical pregnancy or a miscarriage no cramps or clots. My first appt is in about a week and a half what is happening? What should I do?? Feeling sad this is my first time and something I have been trying towards, for a while! I'm feeling hopeless.