Well, you could just say you have a headache or something and that's why you are not drinking. Or you could play the glass switching game - your boyfriend drinks his glass and gives it to you, so it looks like you are drinking. And you give him yours, so it looks like his is full. If you get a refill, you just give him yours again. etc.
In terms of testing, since you are really not sure when you ovulated, I would wait to test until you are late, or AF is due. So I'd wait until the 31st at least. It's probably too early to know right now.
Hope that helps.