Need advice please??!

Alice
Hey guys! I need some advice if anybody can help please! 
I had a MC at the end of July and my next period came on cd37 which I sort of expected as the MC would have messed up my cycle a little, however this month I thought I'd be back to normal but I'm on cd37 and for the past 3 days I have had brown spotting, and I literally mean a few spots a day and when I wiped, it has stopped today so I have taken a hpt thinking I could be pregnant and it is negative.
So I really don't know what to think and hate not knowing what my body is doing. Does anyone know why this might be happening or if I could still be pregnant? 
Thankyou!