what form I need to ask about these underpayments?

Hello, I am wondering what form I need to ask about these underpayments? I live alone with a severe mental heath condition, but I still try my best, and this year earnt myself a 2.1 Bsc Hons. Degree. I recently was sent a pink assessment form, I'm not sure  if it was for esa or pip. But I filled it out and sent it back. Does anyone know what the pink form being sent out is? So, I can make ends meet but I rarely have enough for clothes, which is a big deal when trying to present better and get back into a professional capacity. I thought a remuneration could really help me, and with travel costs to a training course I would like to give a go at. I would like to be a child play therapist/counsellor.  Yes I have a real and severe conditon, but I still try to aim for success! And occasionally get there! And I'm a nice person who also is talented, sensitive and caring. Can anyone advise me where to start on discovering or applying for the under payments that are now being looked at?. I think two years ago they dropped my payments from a support to a work related group, but not for any reason it seemed to me, because I was studying for my degree full time, at the time. I also used to be on incapacity, but also remember a time when I left hospital and was getting esa, but not ela, or something, because I refused to apply for both as I felt one was enough. But I also thought there was nothing wrong with me at the time, because it was early on in my diagnosis. Thanks for your time, S.