What MrsMongoose said. I am a university tutor, so deal with older students, but I would expect you to see the counsellor and get help, I would be happy to help you organise a referral to the correct support service, but I would certainly expect to see paperwork supporting any issue that meant you missed lectures or failed to do yourself justice in exams.
If you failed to sort things out and there was no paper trail to show that you had tried to access help, you might end up having to leave the course with a huge debt and no qualifications.
If you had a job and were late/missed days off work/was unable to work efficiently without a doctor's note, then you would get sacked.
Your idea that adults do not have to answer to others shows how very far you are from being an adult. It's no doubt why people around you keep treating you like a child.
sophie, we do realise you have problems. But you need to start acting like the almost-adult you ought to be at your age: to take ownership of your situation, make sure you get help and support, be active rather than sit around blaming others.