Will I have to be on blood thinners for life?

I am a 21 year old male, recently out of the hospital after experiencing a DVT which originated in my left iliac vein. I had an aggressive operation that removed the massive clot, which was described as being as wide as my thumb and a little less than a foot long. During the operation, the vascular surgeon determined I had May-Thurner Syndrome, which causes compression of the left common iliac vein by the overlying right common iliac artery. I am still waiting to hear on the blood work to determine if I had a coagulation disorder. No one in my family has ever had a blood clot and no one has reported any blood disorders ( I have an extremely large family too ). The doctor was also interested in knowing if I had been taking body-building supplements, which I had been. I had no previous trauma before the DVT, nor had any long plane flights or anything. I have been prescribed Coumadin for at least 6 months according to the doctor. Is it possible that May-Thurner syndrome and my supplements caused the DVT alone, or is it likely that I have a clotting disorder. If so, will that warrant being on Coumadin for life? I have a lot of life to live, and I enjoy playing rough sports. This will be a big adjustment for me if I do.