I am not an athlete by any token, but I do try to incorporate movement into my life. Lately I have been trying to go for walk/jogs and not fast. I find myself having to just walk because the sides of my uterus and obliques are like tight and I feel pulling. I did not feel very out of breath and this was the reason why I had to stop. I am 13.5 weeks. Has anyone else experienced this when trying to run?