I remember doing 2 miles at first too, and being wiped out by it. It was only about 2 years ago, and still seems like yesterday. After a couple more months, I was doing 10-15 mile rides. A year later I could do MUCH longer and harder rides. I'm 54, and was out of shape when I started.
The important thing is that you are having FUN riding, because that makes you want to ride often. The more you ride the more fit you get.
Don't expect to lose weight too quickly- some of the changes will be that you will lose some fat but GAIN some new muscle- thus it may seem like you are the weight yet your shape will be changing slowly and you'll be looking better and your clothes will fit better after a while.
But mostly- have FUN riding!