It may be a sensory relapse, but it sounds pretty unpleasant. When did it start? As I’m sure you already know, steroids aren’t always a good idea, you shouldn’t have more than 2 courses in a year (some now say 3, but it’s your bones in later life that can pay the price in osteoporosis). You can still take steroids for a bad sensory relapse, but it sounds like you’ve decided to tough it out. Steroids work best when they’re taken right at the start of a relapse.
Make sure it is a relapse though, a UTI can give you symptoms like a relapse, so if there’s any possibility that you have an infection, get that tested and sorted out.
You are right that ordinary painkillers won’t help (paracetamol, ibuprofen etc) although some people do take co-codamol. It might help a bit.
It’s neuropathic pain relief you need. You could try a low dose of Amitriptyline (your GP should be OK to prescribe this). It’s basically a tranquilliser in higher doses (say 150mg), but in low doses on 10 to 20mg, at first especially, it can help with pins and needles, burning pain and hypersensitivity. The thing to do with Amitriptyline though is to take it in the early evening, by about 7 o’clock. If you take it during the day you might feel quite dopey and spaced out, and taken too late at night it can give you a hangover type feeling the next day.
Other neuropathic pain drugs include Gabapentin and Pregabalin. Your GP might not be so keen on prescribing these unless a neurologist or MS nurse has prescribed / suggested them (and has been in touch with your surgery to explain what they recommend). So if you have a good MS nurse, you could ask for help and advice.
If your muscles are stiff/tight and/or spasming, Baclofen is a good drug for muscular relaxation. Just low doses again, too much muscle relaxant and you might feel a bit weak.
Apart from drugs, there’s heat and cold. You can get microwaveable heat pads, either gel packs or wheat bags. I’d stay clear of gel packs that need reconstitution in boiling water though, they’re a pain. Some people alternate heat packs with frozen gel packs (or soak a flannel, put in in a sealable plastic bag and freeze it). Or you could use a cooling spray like Magicool. A heat pack might help your back.
Then there’s stretching exercises to help tight and sore muscles. Just standing and rising up on tiptoes can help. Or get therabands (stretchy elastic bands specially made for exercise) and wind one around your foot then gently pull your foot up. I always used to sit on the floor and just stretch my legs out, then touch my toes. Or lay sideways across a double bed with your head over the edge and stretch your arms above your head.
Hopefully some of this might help. Relapses are sent from the devil to taunt poor MSers.