What Causes Hip And Leg Ache With Feelings Of Menstrual Cramps?

Hi, I've had a dull ache in my right side hip area for over a year now. The ache also radiates to my right side pelvic region making me feel like I have mentrual cramps. The back of my legs sometimes ache as well. I've had a pelvic and abdominal ultrasound as well as an xray of my right hip. Everything came back fine. I find that when I sit for a long period of time my right side feels stiff upon standing until I'm fully vertical. When I stand or walk for a long period of time my right side feels very sore and achey and I have to sit down to get some relief. Please help, I'm so tired of feeling like crap. Thank you in advance for any insight.