My DH also used to take a cocktail of painkillers, including Tramadol, as he suffered severe sciatic pain due to a herniated disc (L5/S1). He carried on as best as he could until a day at the beginning of this year when he must damaged the area further following some gardening work.
The pain was significant & at this point he had suffered from this issue for 2 years and so there was no hope that the disc would repair itself. My DH opted for surgery and it was the best thing he ever did. An hour and a half on the operating table and then as soon as he woke up, the pain that he had suffered with for so long had gone. He was back to work after 3 weeks and has never looked back. It took a further month to gradually withdraw from all of the painkillers. His surgeon expressed frustration that it had taken so long for DH to be referred to him.
Anyway, DH found Tramadol very helpful. At his worst he was taking Pregabilin, Tramadol, Naxproxen, Diclofenac (suppositries), Amitriptyline, Diazepam - I think that's everything, hard to remember back now. He also used a TENS machine which he found fairly effective which we bought from Ebay and Max Strength Deep Heat.
So I suppose that my answer is, yes, you can take Tramadol long term, but do investigate the other alternatives as well and it is worth finding out if surgery would be appropriate in your case. My DH also has MS, which slowed down the diagnosis as neuropathic pain was suspected for some time, but it turned out in the end that the disc was to blame all along for all the symptoms he was experiencing.
And one last thing, we did go private in the end and this did speed everything up significantly for us.
Do go back to your GP and discuss the options available to you. You have my utmost sympathy & I do hope that you can get some additional pain relief to make your life a bit easier.