Do childrens services liaise with the college?

I am 17 and left education altogether due to a chronic mental illness that is affecting my concentration. Doctors are refusing to provide medical evidence. No matter how many times I tell them that I can't concentrate (which is why i dropped out) they won't listen. I am 18 in 3 months so why are they forcing me to go back now? I feel like they got involved because I am not in education anymore. I was frustrated that this pain is not going away because I really want to do A levels. How can I get them to leave mr alone? And Do childrens services liaise with the college?