Should I call the maternity unit?

So from around 11pm last night I started getting these pains in my lower back. They would happened literally every few seconds, and last a few seconds. Its still happening now. I’m 33 weeks.

Its like a period cramp in my lower back towards my left. Literally it like fades in and out, so every 10-15 seconds its comes on, then goes again as fast as it started.

Baring in mind I didn’t go into labour naturally with my first so I don’t know what is good or bad to feel.