Hi hun, this actually happened to me when I was 16 weeks pregnant (on the morning of my wedding!). I was so convinced that it was from my vagina that I spent ages calling the maternity unit. It turns out it was indeed from by botty due to piles! There was just so much of it that when I wiped from having a tiddle, it was around the front.
So I would say try not to worry, especially if you aren't having any bad cramping, but call your doc/midwife for some advice. If you're not sure, they may just check you over to be on the safe side.
x