Is it semen or sweat on my underwear?

I woke up this morning with a tiny wet spot, like quarter sized. I do not think it was a wet dream because when I have had those the wet spot is much larger, ew I know, and today I smelled the little wet spot and it did not smell like semen at all. I have no idea what it could be. If it was a wet dream I would think it would at least smell like semen and be bigger, but I also don't know if it is sweat because I don't think sweat would leave a little wet spot and instead I would think it would be a damp feeling. I also don't think it is urine, because it didn't smell like that, it didn't really have a smell, just smelled like the rest of my underwear. Also the spot dried within like 20 minutes of me waking up. Please help me, this spot concerns me because I have an OCD about cleanliness. When I masturbate or have a wet dream I wash my private area about 6 times and take a shower around 2 hours long to get clean, can someone also tell me if that is too much washing and how much washing is necessary to clean off all of the semen. Thank you in advance, and thanks especially for reading this entire question.