recurring spot between my vagina and anus.

Hi all, for the past few weeks i have been getting what looks like a spot which develops under the skin, it becomes quite large and is very sore, and have had to use a needle to pop it (drain the fluid from it). im worried as i dont know what this is. as they are recurring and i seem to get one or two at a time always in the exact same place.

thank you for your info.