What Causes Sudden Tightness In Leg?

Hello, my name is Jennifer. I'm 5'2 and weigh 185 lbs. I have asthma and penicillin and orange juice allergies. i am also on Cryselle for birth control. I have been feeling a tightness in my right leg that sometimes feels like a cramp. I have no discoloration or swelling of the area. I can sometimes just be standing or lying down and get that feeling. Should I be concerned?