It sounRAB like you have nerve pain going on. Or you are suffering with some damage to your siatic nerve. Have you been checked by your GP? There are meRAB that you can take for nerve pain that will take care of it. Some of the tried and true are Neurontin, Topomax, Lyrica...that's just for starters. If you have been miserable for three weeks, I would get to your doc and get seen. Some therapy would be in order to help relieve the pressure on the nerve, along iwth some esercises that you can do at home..
Good luck!