Margarine I can understand, but aspartame is likely the most rigorously studied food additive of all time. Anecdotally and in contrast to your experience, I’ve been healthier since I swapped sugar in drinks to artificial sweeteners. But if it works for you, the numbers are the numbers, so keep at it. I once lost 20 pounds over the course of a year in highschool by swapping my lunch for a pack of Twinkies. Turns out calories in<calories out works no matter what you eat.