I had a bad parent moment and I feel awful.

My child is having problems in school. It's been happening for a while. We suspect adhd and we have been awaiting him being assessed (the wait is 13 months). He has already seen the peds doctor and has been referred out to someone else to be assessed. The peds doctor doesn't think he has it. He said he literally sees kids multiple times that obviously do but for once my son was calm and chill in the apointment room at that time. Anyway, to get to the point, my son is failing language arts. He hates writing. They are doing essays in school (3rd grade) weekly as a test grade. According to the teacher he just sits there and doesnt do anything. So he gets a zero every week. We asked him why he doesn't write anything and he says "he's thinking". We have been trying to work with him getting him to write, but honestly he has a ton of homework everyday already. When is my child suppose to have time to just chill and relax? So anyways, back to the point: I've been telling him for weeks to bring ALL of his graded papers home, or just ALL the papers he has at school. I have even talked to his teacher about wanting these papers. The twice this week he brought 2 papers, and then 1 paper. Yesterday he finally brought several papers, but SO much is missing. He said he has a bin at school where he keeps all of his papers, he said this was all of them. But its not! So I was over my limit. I also have a newborn, 2 months old. A very colicky one at that and lets just say my life is a big ball of stress. My husband is great but holy crap he sometimes just acts lazy with the baby and he also gets frustrated and I feel like its my fault. So I confess, in chewing out my son for not bringing home papers, I cussed at him. I used the worst cussword too. I'm a horrible parent for it. He didn't deserve that. There is no excuse for it. I did it and I suck for it. I just don't know what to do to help and I am overstressed. I grasping for the extremely limited amount of patience I have. Parenting can be so debilitating at times. Thanks for getting this far if you have. I needed to get this off my chest and also calm myself down so I can go back and apologize to my 8 year old for flipping my lid.