Can skinny legs make you weigh less?

Like when I started working out i neglected my legs... horrible mistake! now i work them out everytime i go to the gym which is 2 days then i dont go for 2 days. but anyway my legs dont change much due to my small framed genetics! my upper body is fine though! i have pecs decent arms a 6 pack then you get ot my lower half and its like what is that? i was wondering when i started lifting i weight overall like 125lbs at 5"7 now i'm like 140. people say i look like 150+ and i think i do to! i think i look more then what i weigh! So do you think cause i have chicken legs is why i weight less then i look? and if you can give me any tips on getting legs bigger cause even if i kill my legs to the point where it hurts to walk they never increase in size like my upper body just they increase in strength! plus i dont like squats due to a bad knee but i will do them if its the best way to increasing leg size!!