Hi there -
While there are other potential causes for this sort of discomfort, any sort of pain, tightness, swelling or warmth in the calf should be examined, especially if there is a family history of deep vein thrombosis (DVT) or coagulation issues. SInce you have a positive family history for this and are using birth control, you should have this checked, at least via an ultrasound of the calf and possibly a D-dimer blood test as well, even if you have to go to a walk-in facility to get this done. It's just not worth the risk.
Some other potential problems which could be at the bottom of this are compartment syndrome (more common in athletes, but sometimes occurring for no apparent reason), and varicose or torturous deep veins.
I hope this is helpful. Please update us as to what's going on. Best of luck to you.
John Kenyon, EMT, CCT
Non-invasive cardiology tech, Emergency and Critical Care technician, Critical Incident Stress Mgmt. specialist