Immediately contact ur doc... Low lying placenta may be the reason for little bleeding. I had also low lying placenta but no need to worry, in almost all cases it resumes it's own position.
Cramping can be normal as is "spotting". It depends on color and amount of bleeding. I miscarriage at 8 weeks a few yrs ago. The bleeding I had started dark Brown and within a few days was bright red. The cramping also got stronger. Call your Dr as ad in as you can they can do ultrasound and blood work. It's hard not knowing.