What Causes Diminishing Leg Power, Dizziness, Hands Tingling And Numbness And Clumsiness?

Hi, I have been experiencing diminishing leg power when walking up an incline. I have also been having dizzy spells, pins & needles/ electric senations in the hands, periods of numbness in the hands/fingers, and I seem to be having episodes of walking in a clumsy way....tripping over my feet. I have to lift my legs over a stye when out walking and I have also been having an increase of 'restless leg syndrome' episodes........I am a 51 year old female who has a history of L5 S1 problems resulting in 2 laminectomies and have had to have steroids injected into the spine resulting in the tearing of the spinal sheath.......I am due to climb to the summit of the highest mountain in the UK in 2 months and am concerned about my increasing leg weakness...