@Caroline eek this makes me so excited
Call your midwife team. It could be the mucus plug loosening and but you may want to track what happens next. Perhaps wear a sanitary towel to see what colour any discharge is. Clear discharge once plug has loosened could be your waters leaking. Green, brown or yellow could be sign of infection - hence why pad is useful to track any discharge colour and amount.
I would call triage and ask them. They may want to check your cervix.
I had some pink when I wiped a couple of weeks ago but wasn’t anything - midwife said it might be where baby is engaging slightly more and putting pressure on the extra blood vessels in my cervix, but nothing to be worried about!
These exact things happened to me at this time. My waters broke on the evening of 37 weeks and I had him 37+1. Think I was in labour from 36+5 and it progressed slowly. Good luck! X