Changing flight. Is this a better way? Please answer!?

I noticed that there is 1 hour between my flight and it is in Chicago O'hare airport. I tried to change my departure time from my home destination and I found out that it will cost me 800 more dollars! Is it possible to book a flight earlier with another airline that will be much cheaper so i can get there at least 2 hours earlier or do I have to go by my ticket?