Universal Credit application

Hi I am currently still employed part time, but have been on sick leave since New Year due to mental health conditions. I feel I cannot go back to my job as it is making me more ill and I am not getting any better. Can I hand my notice in and apply for universal credit? O do you get sanctioned if you leave a job even though you are unwell? I have sick notes from my doctor and I am confident she will carry on giving them to me for now. I am worried as I do not know how much I would recieve on universal credit and if I would still get housing benefit etc. I am currently in a 3 bedroom house, under occupied by 2 rooms. Thank you.