What can I do about my mean head of department at college (read more)?

I’m at college to get qualifications to become a teaching assistant, it is my dream job because I have aspergers syndrome and I want to help children like me and with other special needs, but I have a bit of a problem. I was advised by a teacher to go on a course that was wrong for me as I was working within a nursery not a school like I need, last year I did Supporting Teaching and Learning Level 2 but I didn’t get to complete as I started late, so I asked to switch courses back to that one to get the full award, all the Units of work from last year can be used so I only need to do 2 units. We had a meeting with the Head of department, my class teacher and a teacher from sixth form at school and it was agreed that if I can secure a work placement then I could start in the course I want after the Christmas holidays, which I did within 2 days and I phoned to tell her this, however when I returned last week I found out that she (The head of department) is not letting me move until 6 weeks time, making me do work I won’t even need, as some kind of trial because of my lateness. I am late alot of the time because of the bus, the traffic is terrible where I live and the busses are rarely on time, the bus I catch is supposed to get me there 30 minutes early but it gets me there 10 minutes late, so she’s asked me to wake up earlier to get an earlier bus, for someone with aspergers changing routine just like that is very difficult, I have trouble getting on the bus because I have a social phobia, agoraphobia (fear of crowds), chlostaphobia (fear of small spaces/ personal space being invaded) and xenophobia (fear of strangers), I can only get the bus if I have someone I know come on it with me otherwise I get really panicky and shakey to the point of crying, and there isn’t anyone I know who gets the earlier bus. Also she has attitude with me straight away for the littlest things, I told my best friend quietly that I was hopefully moving class as she was concerned about the fact I was unhappy, and she called me to the office and shouted at me instead of calmly saying ‘don’t tell anyone’, she never said to not tell in the meeting and it was my best friend so i assumed it was ok so I didn’t deserve to get shouted at, also she shouts at me because I work at a slower pace than others as I’m dyslexic and it can be difficult for me to get my ideas out and start my work and sometimes I get stuck, but that is not my fault, I feel like she’s singling me out, and that she has one rule for me and one for everyone else, tbh I see this as being penalised and discriminated against because of my ‘disability’/difficulties and I’m wondering is there someone of a higher authority that I can take this problem to? or report her maybe? This is not how a head of department should be like, I’m dreading going back as we have contacted my school to help get me on the course i’m supposed to be on and I’m scared she’s gunna shout and have attitude straight away :/ If you read all of this thankyou and sorry that it this is so long.