Have occasional sharp cramp pains just down from big toe (side/bottom of left foot)for few days now,i drink heaps of water & take a multivitamin hlp

Need more info: since your symptoms state sharp pains it might be a biomechanical etiology causing a possible Tarsal Tunnel due to hyper pronation resulting in compression of posterior tibial nerve. This would be correct if your big toe joint is not swollen and red, this might be getting Gout!! Get some elcetrolytes, for the first put an insert arch support in your shoes preventing hyper pronation.