Hello, thanks for using health care magic. It is a good thing that your STD tests came back all negative. From your description, it is likely that you have a carbuncle which is a collected of two or more infected hair follicles that have joined together. Shaving is a predisposing factor to carbuncles. The most frequently implicated germs are Staphylococcus and Streptococcus and the infection is contagious and able to spread to other parts of the body through contact. Oral antibiotics targeting Staphylococcus are needed for larger carbuncles together with drainage. However, the best option is to see a doctor for a better evaluation and appropriate treatment. Best regards and hope this helps. Dr. Achuo A. M.