The herniated discs most surely would cause the pain and discomfort you feel in your left leg.
When I was 19 I fell down some stairs twisting my back and fracturing it and it fortunately healed but left me with a herniated disc at l5/s1. It wasnt a bad herniated disc but significant enough to cause great discomfort and numbness in my left leg.
At 22 I had a lumbar laminectomy at l5/s1 and felt so much better.
10 short months later (my reprieve) I was in a car accident (i was stopped at a red light and someone without car insurance rear ended my car) and re-herniated l5/s1; herniated l1/l2;l2/l3;l3/l4;t11/t12;t12/l1; and c5/c6. Fortunately for me, the discs that gave me the great deal of pain were c5/c6, l4/l5 and l5/s1.
I had to wait until january 13, 2006 when I was 25 to go to charleston, south carolina (i am from columbia), where I found the most wonderful neurosurgeon to do a laminotomy on l4/l5 and a one level fusion - for now - on l5/s1- after a week I felt wonderful! No leg pain, hip pain, back pain!!! No more pain killers, muscle relaxers nothing! I do have to wear a back brace for approximately 6 months.
I feel so great I am going to let him fix my neck after I recover from this.
I most certainly believe that your leg pain is from the culprit of l4/l5/s1. Find a great surgeon and get it taken care of - dont go through life in pain or doped up on pain killers. I thought I could go through life on pain killers and that is how I totalled a brand new car and was amazed that I came out unscathed.
Good luck!