Congrats on your ride. It will get easier with time, you just have to keep getting out there. Soon you'll be attacking those small hills and making them your *****. When I first started seriously riding, I was tired out after going three miles, and going up this one small rise I thought I was going to die. Now I regularly go up that hill a few times during my morning rides about 14-15 MPH, often in the third chain ring. It's nothing for me to do 40-50 miles or more on a ride, and last year I did my first metric century and even a full century. The only thing holding me back from riding 50 miles a day is this pesky job.