Hello and welcome,
From your presentation this is an abscess
The best cure for an abscess, especially a recurring one is an I&D. An incision and drainage
. If done by an experienced surgeon, it can prevent the recurrence of the abscess and also give a good cosmetic result, avoiding a scar. During the incision and drainage the surgeon also takes a tissue sample and sends it to the lab to rule out the worst.
The surgeon will also start you on a course of antibiotics, mild pain killers and require you to visit him regularly for a short period of time to check on wound healing
and change your dressing.
This should ensure a sterile eradication of the bacteria causing the abscess. This is not because of you weight, it could be because of an infected hair follicle on or around the site of the lump.
Hope this information has helped you.
Wishing you luck in finding a solution.