Thirst that won't go away!

Ok so AF is due on the 7th Feb.. Been ttc for 6 months. For the past 2 days I've had the most uncontrollable thirst! I drank 2 pints of water before bed last night and still felt like I had spent a month in the Sahara! Is this considered a symptom of early pregnancy? Has anyone experienced this and got Bfp? Tia x