There seems to be more than one thing going on here, and that's not unusual in the lower back and pelvis.
Firstly, you say you had chronic low back pain. Now that's different to coccydynia.
The latter is deep down in the buttock crease. If you slide your finger upwards from the anus, you would have felt /be feeling tenderness on deep palpation much lower than the back. Sitting on hard surfaces is often very sore. It's not usually affected by bending and twisting, either forwards or backwards.
However, lower back pain would probably be worse with one or other movement of the back, either bending forwards or backwards, or to the side.
The "Slump Test" would be positive if there is any disc involvement. Try it (type slump test into the search this site function in the navigation bar at C-H) and let me know the result.
Now we come to the groin and inner thigh pain. This points either to a hip condition such as Femero Acetabular Impingement Syndrome or Hip dysplasia (again type these terms into the search function). Or, a pinched nerve high in the lumbar spine would follow the Femoral nerve (or one of its branches: the ilio-inguinal or genito-femoral nerves that go to the groin and even the labia) into the groin and inner thigh. These muscles often become very tender with all these groin/hip/high lumbar spine conditions.
Pull your knee to the chest, and then towards the opposite shoulder. Does it hurt in the groin? A hip condition.
As you see this is all very complex, and what's needed is a careful and very thorough chiropractic examination to find the real source of your pain.
Start by doing the lower back exercises at C-H very faithfully every morning before getting out of bed.
Next, get copies of your X-rays. You can take a photo of them if they are on plain film with your digi camera, with the flash off. If they were digitally made, ask for a copy on CD. Jump up and down and perform hysterically if they refuse at the radiological dept for you to see, have a copy, of your X-rays. It is your body after all!
Then, starting looking for a thorough experienced chiropractor. Ask friends, family, tell your doctor of your frustrations, s/he may be able to recommend someone. Take a copy of this letter.
Good luck, I hope this has contributed. By all means ask more questions.
Dr Barrie Lewis