Tightening while walking

Just wondered if anyone else had experienced this.

I am 35 weeks and lately when I go for a walk my uterus feels like it is tightening up a lot.
On the weekend it happened half way through my walk and today it started after a few mins and I came home after 15 minutes.
I walk on the flat too.

This was happening slightly around 26 weeks too but then I got busy and exercise went out the window. It much more noticeable now.
Anyone have this and did you carry on or stop?

Edited by Babycakes1 - 13 December 2013 at 11:53am