Brief Answer:
Possibly a Pilonidal sinus to be seen by a surgeon

Detailed Answer:
Hi XXXXXXX ! Good evening. I am Dr Shareef answering your query.

Although I would have liked to examine the lesion myself before opining on it, from your history, it seems more like an inflammatory lesion, like a pilonidal sinus. One of the common site for a pinonidal sinus is the area of the present lesion as described by you. The sinus usually occurs due to pricking of hair around this , which gets infected at times giving rise to a tender lump, and then discharging pus if not treated properly ending up in a persistent sinus.

If I were your family physician, I would have referred you to a general surgeon in your area who might advise you with some anti inflammatory drug along with a proton pump inhibitor, an antibiotic initially to control the infection and inflammation. If not relieved, or as a second step further, he might advise you for a surgical intervention where the sinus is laid open to heal of its own from below, or with sutures at some centres. This usually cures the condition. However I would also advise you not to sit on your butts for prolonged periods like a long driving which might be the cause of the hair getting pricked inside the crease.

The pain in your back seems to be a separate entity, and needs to be looked after by an orthopedic surgeon. Your GAD would not cause you problem if you strengthen your will power and add a psychiatric counselling with the treatment.

I hope this information would help you in discussing with your family physician/treating doctor in further management of your problem. Please do not hesitate to ask in case of any further doubts.

Thanks for choosing health care magic to clear doubts on your health problems. I wish you an early recovery. Dr Shareef.

---