I'm not an expert in snakes, but a fluid build up in people is generally from some kind of repetitive irritation (blisters) or an infection (boils, carbuncles, etc).
:/
But none of that sounds like your snakey.
How's the humidity, and the temps? Has he been acting normally other than being tired? No star gazing or cork screwing?
At this point I think what I would do, if it was me, is wait and see if the build ups get bigger, and if they do, POSSIBLY nick one of them with a needle and check if anything drains out.
But like I said I don't know snakes! Wait for someone else to come along and they'll probably know.
Don't jab it just yet.