Will drinking 3 diet sodas a day make me fat? i feel as if i really need to lose some extra weight.

In a way, yes.: Even though they are "diet" sodas, they have actually been shown in studies to promote obesity anyway. It is unknown whether it is the sodas themselves or if it is the food that is often consumed with them (i.e. soda + burger). So you will need to go over what you are eating in a day, count up the calories, and see if that is the real problem rather than just the diet sodas. Good luck!