What Causes Pain In The Pelvis And Upper Thighs?

I am having continuous pain in my inner/upper thigh area of both legs and intermittent pains in my lower pelvic area . I haven't done any different exercise lately and this have never happened before. I also have a very bad headache. It has been 2 days since the last day of my cycle. I jut want to know if I should consider this serious. Thanks