Hi I'm an 18 year old who can completely relate to your situation- Sloppy notes, missed homework, careless mistakes, doodles... you name it. I too was able to skate by until the work load became too much. Unfortunately, as you get older, the teachers expect more and more from you. I specifically relate to your struggles in math- that has always been my problem area as well. I'm sorry that your math teacher has been so unhelpful.

Does your school have a disability office or student services office? I don't know where you are but public schools in the US can provide evaluations for ADHD and learning disabilities and are required by law to provide services if you meet the criteria for a diagnosis. Especially if your teachers have noticed symptoms, I don't see why the school wouldn't evaluate you themselves.

My advice is to continue to try to talk to the school counselor. Make it clear that you want to succeed and ask him/her to help you brainstorm ideas for how to do better in school. Be specific about your problems (maybe start with an example for one homework assignment). Explain exactly what you said here. Unfortunately, going in to your counselor and saying "I can't focus" may not get you anywhere.

Hang in there! I have found that one must be one's own advocate to get anything out of the school system. Good luck!