Oh, missd. Have a totally unMumsnetty hug. (((((missdisorganised1)))))
Your Mum and Dad would be SO proud of you, coping with all this on your own and doing all your studying too. I'm sitting here in tears (! PMT) at the thought of you managing everything so soon after your parents' death. What a lovely girl you sound, your parents must have been awesome.
I hope that doesn't sound patronising!
Anyway, useful stuff: have you heard of Flylady? It's a book about how to run a house for people (like me, for example) who are not "born organised". Her basic premise is not to be too much of a perfectionist - because that way, you'll never get anything done at all for fear it won't be perfect - and to get a simple routine going before it all mounts up and becomes too daunting.
Her website is a headache to navigate, but the the book (despite its weird name) is great.
If it has already started to mount up, DO NOT PANIC! You can get it under control again. An easy tip is to get a kitchen timer, or one on your phone, and set it for 15 minutes. Do 15 minutes in each room - start by going round with a bin, chucking out rubbish. Then do a quick clean with an all-purpose cleaner and a cloth (remember, clean rooms from the top down, do the floor last), then Hoover and/or mop.
Do 15 minutes in the sitting room, then kitchen, then bedroom, then have a 15-minute break. Then 15 minutes bathroom, then hallway, then another bedroom, then rest. Carry on like this still you've done each room. It should tae like 3 hours MAXIMUM.
Don't carry on in a room after the timer goes off otherwise you'll spend all day in that one and the others wo't get touched. Stop and go on to the next room.
You'll be STUNNED how much you can get done in 15 minutes! I always am.
Then set a simple routine for morning and evening. These can be just 15 minutes long too, and include: empty/load dishwasher, empty bins into the main kitchen bin, throw crap away, wipe down kitchen surfaces, wipe toothpaste off sink, put things you need for tomorrow by the front door and (if super-organised) lay out clothes for tomorrow.
Meal-planning is fab and saves you loads of time and money. It's in the book, she tells you how to do it.
I'm really cheering you on, I think you sound amazing.