About four days ago I noticed a spherical lump under the skin, just outside the anus. It is painless, not tender, semi soft (I can depress its shape) and can be moved around quite a bit. Using a mirror I saw that it does not appear to be red when pushed to the surface of the skin. I have had some constipation, but there is no visible blood in my stool or on the paper. There is no swelling, itchiness, redness or discharge, and I have not had a fever. I am a 27 year old heterosexual male with no known diseases. I am a healthy weight, but am sedentary for much of the day. I am very worried, any help would be appreciated.