"How far along are you?"

So the other day someone asked me how far along I am. I usually tell people in weeks, not months. It's partially because I know weeks is more accurate and most people don't realize that a pregnancy is 10 months, not 9.

That being said, I am 16 weeks, having completed my 4th month and started my 5th. Would you tell people that you are 4 or 5 months?

What do you tell people?