Brown discharge with mild backache - 27 weeks 3 days

Hi I’ve spotting at 20 weeks and 24 weeks. It was light pink /red. Went to AnE but they said it’s not from the placenta and baby doing fine so far. Now I’m 27 weeks 3 days and I’ve had 2 episodes of brown discharge. Today and also 2 days ago, this time with mild backache. Anyone experience same thing before ?