It is indeed a common sign, but do mention it during your regular doctor checkups. If there is any itching or burning, your gynac might need to give you a safe cream.
From what I remember, increased discharge happens because of estrogen changes. Just make sure it doesn't smell bad or cause itching, as that could be an infection.
I totally understand how every little change makes you wonder if your miracle is on the way! Yes, thin white discharge is actually a very common early sign of pregnancy.