You sound like me when I started riding four months ago. My progress has been slow, but I am now seeing some results. I was disappointed at first and thought about quiting. Two weeks is not enough, keep hard at it, and find some flat terrain as others have said and the results will come.
I'm 45 years old, 5'11" tall, 195 lbs. I have never exercised in my life. Terrain is fairly flat here. My first ride was five miles and this nearly killed me. I ride 4-6 days a week since I have started. I am currently up to 10-20 mile rides during the week nights with a 35 mile ride on Saturdays, I know this is not a lot of miles but for me it is huge. My weight is now around 178lbs and my waist is about two inches smaller, I also feel a lot better. I used to be dead tired by three in the afternoon, now I ride 10-20 miles most evenings after work and enjoy it. I also ride compact gearing, and it has been plenty of gear for my area.
Keep with it, and remember that it takes time to get in shape. It took me 45 years to get in bad shape, so I know that it will take time and determination to get in good or great shape.