24 weeks 3 days with cramping? Should I be concerned?

So I'm 24 weeks 3 days and have this crampy feeling in my lower abdomen you know that cramping you get in your sides when you run for a period of time when you arent used to running that's how it feels. I dont feel it when sitting only while standing/walking. It started yesterday but its became worse today. I'm not sure if I should be concerned i don't remember having this with my first pregnancy we have a prenatal visit tomorrow morning. Any advice or opinions welcome.