What oh what should I do????

I am a mother of two incredible kids and I know that every mother says that and for them such as me it is completely true. I have a son who is going to be 7 and a daughter who is three. I really live a great life with them and have had many an opportunity to teach them and learn from them. But in recent months i have been struggling as a mom. My son is very active and a bit unruly a lot but the thing is that you can tell there is more to it then just him being a brat. he struggles with paying attention and definitely works off of impulse. he has just entered 1st grade and only 2 weeks in we have started to have trouble. He can't even pay attention in small groups and is affecting the other kids in his class as well as being behind in his reading skills. he gets frustrated and angry when he doesn't understand something because of not being able to focus. What I think is the most difficult with me is having a hard time deciding what is him just being a pain in the ass kid as they can all be or something that is beyond his control.
Yesterday he got in trouble for teaching a boy from another country that doesn't even speak English how to spit milk out of his straw at other kids and he does know right from wrong he isn't dumb and when not in the situation can tell you that it wasn't right but just makes bad choices in the moment and I am at my wits end! I have looked into many different things that I can do and have discussed with his doctor and are in the process of testing which takes so long....

Inattention:

• fails to pay close attention to detail or makes careless mistakes in schoolwork or other activities
• has difficulty sustaining attention in tasks or activities
• does not appear to listen when spoken to
• does not follow through on instructions and does not finish tasks
• has difficulty organizing tasks and activities
• avoids or dislikes tasks that require sustained mental effort (e.g., homework)
• is easily distracted
• is forgetful in daily activities

Hyperactivity:

• fidgets with hands or feet or squirms in seat
• does not remain seated when expected to
• runs or climbs excessively when inappropriate (in adolescence and adults, feelings of restlessness)
• has difficulty playing quietly
• is constantly on the move
• talks excessively

Impulsivity:

• blurts out answers before the question has been completed
• has difficulty waiting for his or her turn
• interrupts and/or intrudes on others

Any feed back or anything that people know that they have experienced I welcome your commments