weight loss?!

i've put on a 23lbs in the past 6 months due to some medication i'm on. i'm currently on a diet and doing exercise every day but will it make a difference? or will the medication make me continue to gain weight anyway?

also, i'm 20 years old and 5ft 1ins tall. how many calories should i be eating in order to lose weight? cos i think i should have less calories and loads of exercise to lose it, but i've heard you have to eat a certain amount of calories to lose weight? confused? i definitely am. 4 months ago