You can take one now.
it might be more accurate if you go at LEAST 2 hrs (if that's as long as you can hold it) just hold back on the fluids a bit first... maybe 20oz or so?
But take one now just to be safe! :) that way if you do have low prog. you can call your doctor ASAP in the morning so they can start you on progesterone supplaments.
I'm constantly thirsty and I remember this with my last pregnancy I was using the restroom every 2 hours or less. Two hours is the max I can hold it it seems. I don't sleep more than two hours before I'm up running to the bathroom either.
I work graveyard so I'm not off work till 7am and I wont get up till 2:30 then back at work at 5pm I really didn't want to wait till tomorrow afternoon to test.
My dr said to test the day I miss a period if I ever thought I could be pregnant since I had low progesterone last time. He wants to start me on prometrium as soon as possible.
I would wait until the morning. If you test then, and since you are two days late you are more likely to get an accurate result. Then again, you could wait a few more days. The longer you wait the more likely you are to get a positive result if you are pregnant. It's up to you, but either way I'd say test in the morning, especially since you have been drinking so much.