I get in the drops and go a couple gears lower.
Maybe you are trying to push too high a gear. Start with a gear such that your cadence is 80 rpm.
You may also be in poor fitness. 1.5 miles several times/day is not going to get you in shape, unless you push yourself hard every time. If you avoid sweating, you are not pushing yourself at all. Just cruising 1.5 miles on a bike has about as much exercise value as walking around the block.