Yea see the doctor and find out what you're not taking in from your current diet. A regular check up caught the fact that I lacked B12 in my diet, my body just doesn't take it in and I felt like total shit all of the time. A year of monthly B12 shots and a supplement everyday with breakfast sorted me right out.
For food I eat the diet my Grandparents ate while also being proactive about making sure the food I was buying wasn't laced with a bunch of sugar. I keep a small vegetable garden and various fruit trees in the yard. I opt for a piece of fruit instead of junk food for snacks. I eat a ton of meat and food generally considered bad like biscuits and gravy. The trick is I actually do the same workload that they did back in the day. A lot of the bad food isn't so bad for you if you actually make an effort to use it for fuel instead of sitting around. Most of the meals I eat are home cooked but rarely (once a week) I'll eat fast food or pizza.
It's an individual thing for sure. Get with your doctor and find out what you're lacking and adjust from there. The main thing is to avoid the junk food, soda, and the fad diets. I was addicted to soda to the point it was all I drank. I couldn't give it up totally so now I drink homemade sweet tea instead but I mostly drink water while working during the day. The tea is reserved for meals and a treat after work. Diabetes runs in my family so I just cut out corn syrup from my diet. If I can't find it with real sugar I just don't eat it. After cutting it out I've noticed I don't feel like shit nearly as often. Regular sugar doesn't do that to me.