Pre Workout making me feel like crud afterwards.

I only use pre on Sundays when I go to the gym in the afternoon. Other days espresso. I suggest your start with way less than a full scoop. I use 1/2 of some shite called "Total War". It's more than enough.

C4 is a low grade Pre workout supplement. Find a clean pre supplement like Transparent Labs that uses multi versions of 'caffeine' to make you come down slow and steady and do not buy one that has a proprietary mix that doesn't list out every ingredient and the dosage.