35 weeks pregnant and weird symptom?

Hey everyone. So I'm going to be 35 weeks tomorrow. I've been having a lot of cramps for a week's now but I know they are normal. My problem is that a couple of days now I'm getting this weird cramp or pain some time to time when I walk down on my vagina it goes from my pelvic to my vagina and it really hurts. Is not all the time but it is very painful for like 10 sec and once I sit down then stops and if I get up again then I might get it again. Anybody knows what is this and why? Should I be concern?