Without being funny everyone will soon come along and recommend random supplements. You just need yo go to the docs and see what you are lacking. Its a simple blood test. It could be iron, vitamin d, zinc, or absolutely anything. Either go to the docs or take a good multi vitamin and mineral tablet.
Beeb is right, however you should also examine what foods you should avoid
a lot of popular processed foods actually harm your body, there are twenty foods listed in this website with all the reasons for not eating these foods!
Try to juice or drink green smoothies. Take a multi vitamin and some sort of fish oil. You should get bloodwork done just so you know what deficiency your body might have and go on from there.
Sorry folks I should have mentioned had a complete set of bloodtests incl LFT,KFT, tyroid and so on. Nothing showed up as low/high so GP has basically dropped the issue for now.
a good diet will cover all the essential vitamins. doesn’t hurt to add a vitamin supplement but it should never be a replacement for a healthy diet so dont rely on just a vitamin supplement for energy. try eating fresh fruits, and veggies.