Trying to cope...Advice Needed

I honestly don't what to write so I'll just tell my story briefly and hope someone here can offer me some suggestions and helpful ways to cope. Well I have been married for two years to a man I believe has ADD/ADHD. I am not qualified to diagnose him but I have done significant research on the subject and I couldn't find one symptom he does not possess and it is driving me nuts. We are a young couple I am 27 and he is 25 with a 4 year old child. I thought that a lot of his issues were due to immaturity but believe that there is some underlying issues. 
When we first met he wasn't the neatest, clean, and most organized person but I thought that was because he was just use to being a single male. But then I started noticing how he cant seem to focus when we are having basic conversations, understand simple concepts, and he cant keep quiet long enough to allow me to finish speaking my thoughts before he interrupts me and starts responding to something he thought I was going to say and he is usually wrong. Any task I ask him to do no matter what it is cleaning the kitchen, running errands, hanging up clothes are all usually done half a##. The other day I asked him to clean the kitchen, and when I go in there the counter is not wiped off and there is a pan, cup, plate, and spoon in the sink. When I ask him why didn't he just finish those four dishes he tells me I'm always nagging, I'm petty, and in the middle of his rant gave me two reasons why he didn't wash them which were he forgot and he was tired.  I keep all my stuff nicely organized and know where all of my stuff is, he will use my belongings wont put them back where he found them and then when I go use them I cant find my stuff and neither can he. Anything I have a problem with results into me being a nag and I don't know how to let go of little stuff. I am very angry, tired and fed up, however I'm not ready to give up because I love him, my daughter loves him, and we sometimes have very good times together that make me feel like there is hope. On the other hand I feel like I need to be on drugs to deal with him. I have read some other stories on here and it is nice to know I am not alone. We have a therapy session coming soon and I really hope it helps because I am holding on to this by a thread.