Lol this is not anything bad. I am a woman and the same thing g happens to me. I have also had anal sex enough times to say that the anus excretes it's own sort of cum like fluid when aroused. The male has his own G-spot which is located at his prostate gland, if any of you feel the curiosity to explore, definitely Google it. The Anus isn't as scary and dirty as many might think.
I am almost 30 and my anus has been getting wet during masterbation since I was in my teens. It only happens during masterbation or intercourse, being aroused mentally or just having an erection is not enough to trigger it. The fluid is clear and is not thick, it looks and feels like sweat. Mine has no odor like others have described, but I keep my anus very clean. I actually wash with soap and water after every bowel movement. I am a straight male and have no interest in anal play. I've tried it a couple of times but it doesn't feel good to me. When I watch porn it is mostly girl on girl stuff, or occasionally guy on girl. Guy on guy doesn't interest me. More power to you if that's what you like but it's not my cup of tea. I have only ever been with women. I haven't ever told any of them about this and my current partner has never noticed. I have been baffled as to why this happens to me. Sometimes it will go away for a while (it seems to be whenever I have a job that requires me to be more physically active). I am 160 lbs and 5'10" so, no this isn't because I'm obese or anything. I really would like to figure out the cause because I want it to stop. I don't like strange fluids leaking out of me with no apparent explanation.