What can I do to get rid of constant and severe leg pain?

Evaluation. You need to be evaluated by physician to rule our peripheral vascular disease, nerve compression or some other abnormality in order to offer you a solution. Smoking, diabetes, hypertension can be contributing factors.
Multiple causes. Need more history of start, location, other issues. Be examined keep your record of when, where, why, how to share with your pcp. He may have you see vascular surgeon, or orthopedist depending on the story, findings, and some ultrasound testing. Usually with a diagnosis, good treatments can be identified.