Please go and see your GP and tell him/her how you are feeling. You need help to deal with all of this and counselling and/or anti-depressants can make the world of difference. Let someone help you. You can't do this alone at the moment.
It would probably also help to get your meds reviewed - there may be a better balance that would help with your symptoms more?
And perhaps your GP would nag your neuro to get you on a drugs trial for SPMS. Tysabri CAN improve symptoms; it's the only one available that can. There may be new ones coming through too that are being trialled.
Re DLA - are you a member of the benefitsandwork website? If not, please join. It costs about £20 for a year, but it is worth every penny. Read everything they have about DLA before you do either a new appeal or a new claim. It's all in the wording: if you know how the forms are assessed, you know what to put so that your symptoms and disabilities are assessed properly. You also need to have at least one really good supporting statement from a medical professional - either your neuro, MS nurse, GP, physio, OT, etc, detailing your worst symptoms and how they affect your life. There is no way that someone with SPMS and who has your symptoms should not get DLA.
Most of all, please don't hurt yourself. If you get the right help, things really will get better.
I have to go out now, but I'll be back later. If you want to talk more privately, please send me a pm and I'll get back to you as soon as poss.