Reading your question, I agree that you should not have this much pain if your hip is fixed, especially at your young age. My first thought is that there is
something else causing your pain, such as sciatica, which is a painful nerve condition of the hip/buttocks on one side of the body. My other thought is that your hip may have osteoarthritis which is causing pain, especially since you had an injury.
If you have not had a second opinion from an orthopedist, I would get one. They may want to check xrays or even a MRI to evaluate your hip joint to make sure everything is OK. If you have already gotten a second opinion and they told you everything is fine, then I would try to go to a Pain Center, so they could evaluate you to see what is causing your pain.