Do I need to wash my down bag?

It does, but this was definitely perspiration.  It was inside the sleep bag not outside.  

Ok so here's the whole story, and it's a bit embarrassing but I'll tell it anyway.  So the trip was a two day car camping trip with some friends.  The first night around the campfire I had a "bit" of "extra alcohol" (don't usually do that) to the point where I felt pretty messed up most of the next day.  I had no problems with sweating that first night, just the massive "been run over by a truck feeling".  The second night after I spent the day rehydrating and was feeling pretty good by bed time was when the massive sweat incident happened.  What I'm unsure of is if that was related to the night before and it's after effects, the fact that I had the rainfly closed up on the tent during the day to keep some gear out of view and it was warmer inside than it could have been, the ambient temperature (although actually colder than the first night) or a combination of all of it.  

I know someone asked about ambien, nope, but cpap machines probably have a similar effect of helping you fall asleep quick, and it's definitely a deep sleep.  Combine that with lack of sleep from the previous night and yeah that's a recipe for falling asleep really quick and hard.

A 20 degree bag is going to be pretty darn hot on a 60 degree night. Other factors may be involved, but I'd say that you were definitely overdressed. Yes, using it like a quilt can help. Leave an arm or leg out if needed, or just scrap it and maybe use a light jacket or something.

1) Altitude is generally colder at night.

2) Humidity holds heat in the water molecules (there's generally less humidity at altitude).

3) Clouds, especially low dense clouds, also help trap humidity. A large low cloud cover will mean higher humidity and probably greater warmth, regardless of altitude. A clear sky will mean lower humidity and colder temps, regardless altitude. Take it from a guy who's lived near sea level all his life, but has forayed as high as 14,000 ft.

So in the mountains of Tennessee in the summer on a cloudy night you might be pretty warm, wet, and sticky (ask FamilySherpa, @tdale , and others). Even low lying areas like where cajun lives seem warmer because of the high humidity.  And yeah, it can be really sticky, which is why they don't backpack/hike in the summer.

Even where I live (sea level, Maryland) a high pressure system behind a summer storm can bring welcome relief - fewer clouds, lower humidity. Well, relatively speaking, anyway.  A clear blue sky after a storm can be a beautiful thing...

BigLoad, I do it pretty much like you with my WM Apache.  Rarely camp/sleep anywhere temps are over 40F at night.

OP, I did not mean to cast aspersions with my reference to taking ambien and have no clue about CPAP.  If you really were drenched in sweat, it might be a good idea to have the bag washed.  You can do it yourself but I'd recommend Rainy Pass for professional cleaning.


rainypass.com

By the way, is that a boxer in your avatar?