How much? What tangible results will you get in your life? How much extra energy, as well as money, will doing healthier eating cost? How much time spent doing less fun activities?
Do you think that you felt bad because of guilt or stress about unhealthy eating, or do you think the food has a physical effect on you that’s noticeable the same day? If a physical effect, which ingredients cause it by what mechanisms?
This doesn’t sound specific enough to be very motivational.
How much money would you save per month? What would you buy with it instead? Do you know how many dollars per month you spend on food now and in what categories (eating out, frozen microwave foods, whole foods, etc)?
Overall, I suspect that you aren’t doing it because you aren’t very persuaded because you haven’t thought it through in detail. You could use more knowledge about it and don’t actually know enough yet to reach conclusions. This idea of understanding things in more detail before expecting to be motivated to do them may be useful for @LMD too.