How can i motivate myself to get fit to boost my confidence, health, and happiness?

Im about 6' 2", 260 lbs and tired of being out of shape. I desperately need this change in my life for confidence and health. However, in this goal that i have set i am my own worst enemy. I keep thinking positive about how i can do this and how good it would be, but i can never motivate myself to go for a run or try to join a gym. Im stuck in this routine where i wake up, do anything that i want and just tell myself there is always tomorrow. I'd like to get fit by sometime in late august, so when i go back to school i feel prepared. Im really nice, considerate, funny, (and humble) and i think that if i were to change myself on the outside in a positive way, people may want to see what i look like on the inside too. This is really important that i get this done but i just am struggling with it. Any help or advice would be really useful.