Cramp after squatting

I am 20 weeks today and i went to a public toilet and could only allow me to squat. When I finish peeing and stood up, I felt cramp at my lower abdominal and it felt cooling at that area for awhile and then my spine was aching .. 3-4 hours later, my stomach is still a little cramp… fellow mummies ,should I be worried ? There is no bleeeding as I have checked ..