Oh nannon, you really need to think of you. redhead is right, you should come first in your life!
Thought I hadn't seen your name for a bit, and it's no wonder, when you are under so much stress.
Already you have identified that your boss is unappreciative; I honestly think if you took time off it would make your management team see how much work you do. A job is a job hun, and they will have to find way to manage without you temporarily, otherwise they will be managing without you permanently.
It is so unreasonable to pile this on you, and you should NOT be doing work at home, under any circumstances. It really demolishes the work/life boundaries, and this is how stress and so on comes about.
You should get company sick pay followed by statutory sick pay if you are off for any length of time (I think that's the right way round!). Either way, you shouldn't be left struggling.
You need to write down all the concerns you have with your work, as it seems your management won't take it in verbally. Also, it helps me to organise things in my head by writing them down! You could write a formal letter, copied to the MD, and your supervisor, or just a communication to your boss.
Take time off, PLEASE! Take advantage of the sick note ASAP, you really need it hun. And when you do, have a few days of doing nothing and relaxing, and a few days thinking about what you love doing, and how this could translate to a job. Visit Connexions if you like, they could do a job search that takes into account all your skills, talents and passions I think.
Let us know how it goes.
xx