sharp left ab pain

Ladies I'm 18+4 weeks along and today I've been feeling some sharp pain in the left lower abdomen especially when I was walking at the grocery store. They eased when I sat down. Now, some hours later I felt them again just when I walked to the toilet, but I don't feel them when I lay down. My baby is on the right side and I feel him moving so I think it's unrelated to the baby. Do u think it's normal to have such pains or should I run to the ER? I can't quite walk when they start. Thanks in advance!!!