Hello, Welcome to healthcare magic, It could be herpes genitalis , which is a sexually transmitted disease. Grouped fluid filled blebs which is painful is the typical herpes lesion, which breaks down to form shallow ulcers. It could also be boils ( folliculitis) which is a bacterial infection of hair follicle. I will be able to differentiate the two if you could upload a picture. You may ask me a direct query by clicking on this short url http://bit.ly/dr-j-chacko , where you have an option of uploading a picture of the lesion which will help a great deal in diagnosing the condition. Hope this helped, Take care.