Pain in leg

I've been having this pain in my leg. I had it the beginning of this pregnancy then it went away for a few months now it's back. I did tell the dr she doesn't think there is anything to worry about. I'm having my section on August 15 and of course my mind is wandering to a blood clot so I'm a nervous reck. Also there is no swelling or pain when I walk. It's usually when I sit.