My right thigh has been numb for 2 weeks (more or less) from my waist till my knee and my lower back is hurting. i went to a neurologist and she gave me an injection and pills of antibiotics cause she said its an infected nerve but im still in pain?

I am not certain if you have infected nerves or not as per the neurologist that examined you, however not all infections could be treated with antibiotics. It could be a virus or it could just be inflammation of the nerves not related to infection; you may want to obtain second opinion from a medical person the could comprehensively evaluate your situation.

The most likely explanation is meralgia paresthetica, which represents a nerve compression at the hip associated with tight belts around the waist or being overweight. This is not due to an infection, in 99% + cases. Low back pain can be associated. A second opinion is advised.