I'm afraid it has been a fair while since you posted and it has taken until now to get a second reply. I'm glad you have already met Sophie_M who has given you a number of very useful links, I'd hope you have had a chance to explore a few.
The delay is nothing to do with you, or the subject of your post - which is important. It is simply the system does not always work as we would like -sigh.
After reading what you had to say I think you are being too hard on yourself. After all you hold down a job, not always an easy thing, and wish to have a clear direction to steer. You also sought help when you were able - a sensible move.
I'm sure you realise that your problems in years 11 and 12 were due to the passing away of that peron who loomed large in your life and was always there for you. Grief and loss are not something that disappear quickly, and the more a person meant to you the deeper the grief. It can affect your feelings and actions in all sorts of ways, including not being motivated or able or concentrate. The passing of my partner did this to me.
Of course once your started to not perform for a while it gets harder and harder to catch up. You did seek help, but at that stage catching up was not an option - which is not to say you cannot lead a productive and happy life, just perhaps not in the way you originally planned. At 18 things are flexible, which is both good and bad
Good becuse there are lots of different paths, bad precisely because there are so many paths it's easy to fail to see one that suits, leading to your current worry about having no direction. My own experience for what it's worth is a door will open when it and you are ready. Do you have anther liking within your reach you might wish to follow?
I can understand it is easy to slip into giving the impression you are at uni. Is this because your dad and brother would really hit the roof and not understand? I'm sure it is not good for you to keep up this pretense, firstly because of the ongoing danger of discovery, but secondly and more importantly it says to yourself you have something to hide because you are doing something wrong -which you are not!
It's OK to have a job and not study right now. Things may change in the future, fine, but now you are really recuperating still and need to cut yourself some slack
Do you think you might confide in your dad or brother? That way you might have an ally who can give you perspective and support
I hope we can talk again