Hi @ronyb and welcome from me too
As you've already noted, MS can be notoriously difficult to diagnose, especially when so many symptoms might be due to a different condition. You say you have cervical spondylosis; I take it you know it too can also cause things like numbness and pins and needles in legs, feet, arms, hands, and things like neck ache and headaches? It doesn't specify facial numbness as a potential symptom, but I've heard of others with spondylosis who've had facial numbness.
That said, the facial numbness you describe is something I had once (and some other MSers too), on the right side of my face, in the year leading up to my DX (when I was 49), when it was initially thought to be Bells Palsy but neuros later said it wasn't, so I was left to believe it was due to my MS. In my case, it lasted about 3 months, then went away and only returned once for a much briefer period of just 2 or 3 days and it was much milder.
Low back pain in MS can be due to changes in posture as a result of other MS symptoms or reduced mobility. If possible, an MRI of the lumbar region might help to see if there are any non-MS problems, eg, with discs?
I also have cervical spondylosis, and other lumbar spinal issues (stenosis, disc problems and more). This makes it even more difficult for the specialists to know whether it's my neck/back or MS causing some of my symptoms. In some instances, the back problems can exacerbate my MS symptoms and vice versa, eg, an achy pain in my right thigh. One example that I have right now is intense internal vibrations (like an earthquake!) in my feet, legs and abdomen; and right now, I don't (yet) know if it's due to pressure on a nerve in my back or neck or due to MS "neuropathic pain" as I haven't yet asked my specialists about it. I now have terrible posture due to pain from my back and other pain, so that falls into the secondary type of MS pain due to change of posture.
I can totally understand your not wanting to miss out on your fabulous 50th birthday gift! Might it be an idea to maybe first check with the specialist or doctor who deals with your neck spondylosis? If it is due to your neck, then it wouldn't be an "undiagnosed condition"?