You may have a condition called hidradenitis suppurativa. In areas where the skin rubs together, such as in the groin or armpits, sweat glands and hair follicles can get blocked up and infection can develop. Small lumps or even big abscesses can result. The swellings can rupture and drain pus, as you have experienced. Obesity can aggravate the condition. You have also noticed that eating fatty foods really aggravates the problem, so avoiding them and losing weight are things you can do to alleviate it. Warm compresses may be soothing and help infections come to the surface and drain. A sizeable abscess may require a doctor visit to open it up and drain it properly. Hope this answers your question.