Regular tightenings at 33 weeks

Just out of curiosity, has anyone had regular ‘tightenings’ of the tummy.

I was in hospital on a CTG the other week and they noticed that they were consistent, and fairly strong and regular. Which is apparently not Braxton Hicks. Was kept in overnight and given some panadol and discharged the next day after an ultrasound.

I still get them regularly (almost daily) and just as strong. They said it’s very unusual and to monitor closely.

Has anyone else had this and do you know why?

Ps: did do some sort of swab that indicates pre term labour, this came back negative so they weren’t super concerned. Second baby and didn’t have this with the first.