Re: Does this sound like ADHD or something similar?
It sounds like it could be. It also sounds like it could be something else.
A couple of things to keep in mind-
1) He has to exhibit these behavior patterns in more than one environment for a clear diagnosis. ex school and home
2) He is extremely young to end up with a diagnosis quite yet.
With this in mind, you don't want your ped diagnosing him. You want a psychologist/neuropsychologist here. Even if there is no clear diagnosis, you can absolutely find a therapist who can help you help your son. (because at this age, that is how it works)
I think the pottying and penis clutching is unrelated. Many children, boys and girls, do this kind of thing and are neurotypical.
Do you ever get to see him in peer group settings? That is where I saw differences in DS1 starting around age 3, but it wasn't until 8 that a diagnosis was in order.
FWIW, the writing/coloring thing is a bit soon to worry about. My eldest (ADHD) didn't ever like coloring until his fine motor skills were much better developed around second grade. DD (who is definitely not ADHD) didn't color much until 4.5 and then something clicked and she became a coloring fiend. DS2 (just turned 4 this summer) isn't much into coloring either but I am seeing a slow change in him recently where he will color small areas in detail. A large coloring picture is too much, but a small figure that takes 1/4 of the page is more doable for him.
Melissa-Wife, mother to DS 4/02 and DD 4/07, DS 7/08
ISO: my lost shaker of salt