Why do i feel so tired with no energy on the days that i don't go running? i will feel terrible and then as soon as i go running i feel great.

Running: that is a good news. People feel the other way. When u exercise there is adrenaline rush which will make u feel energetic. There is also increase in levels of endorphins which will help you to feel good.

Exercise!: The benefits of regular exercise such as running are many and well-researched. Cardiovascular activity boosts the immune system, increases blood flow to your brain and tired muscles and releases "feel-good" molecules into the body. The biggest challenge is getting over that initial "I don't feel like it" block because, as you identified, as soon as you exercise you feel great!