tingling in feet and neurontin

Hiya iv had tingling i feet 5 yrs and in part of my back 5 months, had mri all ok and nerve conductive test all fine, doc has put me on 300mg of neurontin a day for 2 weeks then to up it to 600mg in couple weeks only been on 2 days, i still dont know if ms would they of found something by now in mri and nerve test? i get tired quite alot and my feet swell alot through out day too which feels like they are burning, i am sick of it all am 30 next month and hoping it works but i still wish i knew what the condition i have is anyone else any ideas? or taken neurontin how long does it take to work??