What Causes Pulling Sensation In Back After Change In Diet?

Hi, i ve recently changed my diet. I m lactose intolerant so i have cut out all dairy and also caffeine and have added more fruit water, lean meats, brown carbs and pulses and legumes to my diet. Overall i feel absolutely great! However since starting this (on monday) i ve felt this uncomfortable ache, like a pulling sensation when i bend down or over in my lower back, back of thighs and back of calfs...am i lacking in something? Or have i had too much of something? My mother thinks its too much lemon, which i have overdone? I d like some advice as i want to begin exercising without this pain