Is this a good workout?

I've been doing about 2.3 miles everyday - 1/3 of a mile for warmup, then I did a mile, rest, and do another mile. I'm pretty tired after the first mile, and very tired after the second. I've been supplementing this some of the time with about 30-40 minutes of biking afterwards. Is this sufficient for getting in a lot better shape in a few months?