S.B.
If he's sitting down, he might not have good control over where it goes. It might be something as simple as that.
I have a son, I have a nephew, I've done daycare and have lots of experience with little boys. Even when they stand up to pee, a speck on the wall can distract them and their aim will go out the window. Not exactly literally, but.....
Aiming and shooting straight certainly takes practice.
I hope everything goes well with the pediatrician, but I actually think things will work themselves out once he begins standing to pee. My dad taught my son and nephew how to do it when they were itty bitty. They went on a little walk and they had a special rock in the yard he showed them how to aim and pee on. He also built little stools for them to stand on in front of the toilet so they could pee standing up in the house without whizzing everywhere.
Let's face it....even if it comes out straight, if they aren't aiming right, it's like a fire hose gone crazy.
Best wishes!