We've been having similar problems with our son. I have severe ADHD (and other stuff...) and my 5 1/2 year old was diagnosed with SEVERE ADHD and ODD (Oppositional Defiance Disorder) right after he turned 4! Doc said, "in all my years in this profession, I have only seen a couple other kids that were so young and had it so severe!" That made me feel great (dripping with sarcasm), especially since he was old and had obviously seen A LOT of kids! ARGH!
But seriously, back on topic... :) We started him on Focalin. First 2.5mg 2xday, then other doses, and are currently on Focalin XR 10mg in AM, Focalin 5mg in early afternoon, then Clonidine 0.1mg at night. He has been having that anixiety too. Wakes up screaming in the middle of the night, and nearly every night ends up in our bed with us. Won't even go into the bathroom anymore by himself to brush his teeth, or to go potty, or anything alone - he always has to have one of us with him. It's gotten to the point were he's started going potty in his pants again if we don't get there in time, and this has even happened at school! He's in Kindergarten, and he won't even tell anyone, he'll just sit in his chair and pee! The teachers will only know when they see the puddle under his seat! It's not every day, but about 2-3 times a month. I know it sounds crazy, but it's all because he's scared! If he says something to the teacher about needing to go (it usually is a quiet wisper, not a speaking voice) and they don't hear it, or can't go with him, then he's too embarrassed to mention it again...and will just go in his seat and sit in it... It seems like that would be more embarrassing, but he doesn't see it that way...
He's gradually (very slowly) gotten better, but it's still there... I'm on Adderall XR and have found it's the only one I can take, that doesn't have any major side effects for me. I've wanted to switch my son to it too, but because he's so young...I wasn't sure.
Anyway, one thing that has helped with the anxiety is the Clonidine. I, now, will break it up and give 1/4 of a pill in the AM, 1/4 in the afternoon, and the remaining 1/2 at night. It's helped a lot for him. Just a warning though, if you decide to try it. The Night-Time dose will make him very tired, especially at first, so make sure you give it to him within 30-45 of bedtime and with food. Also, it'll effect the mornings too. If he gets up really early, you'll need to give it to him earlier because I'd say, from our experience, it needs approximately 11 hours before he needs to be functional. We had to adjust all our dinner/bath/bed times in the evenings because if we wait to give it to him too late (approx 7pm) then he is SO CRANKY (putting it nicely) in the mornings! We get him up about 6am, and if he gets his night dose before 7pm, he's ok; but God-help-you if you wake him up too early or give it to him too late! HA!
Well, I'm not sure if any of this is helpful... HA! I think I got off track a bit (Normal) HA! :)
At minimum, at least you know there's someone else out there that's been dealing/still dealing with similar issues! HA! At least your son isn't pottying in his seat at school and sitting in it! (I hope it never gets to that point!)
Praying for you, your son, and your family! :)
Jessica (JJJ ADHD MOM)