I started commuting on my mountain bike, I didn't want to invest in a new bike until I knew I was going to stick with it. It wasn't good, the bike was heavy, the gearing was wonky, and the geometry was all wrong.

As others have mentioned above, upgrading to a road bike is really the only way you are going to get rid of that "I feel like I am going really slow" sensation.

A road bike is going to give you skinny tires, a much more aerodynamic posture, a tighter gear cluster, a more comfortable geometry for long distances, and more hand position options. I could keep going.

If you are serious about commuting and believe you are going to stick with it, you really should consider all of you specific needs and find a bike that will satisfy those needs. If this is a temporary commute while you are in college, I would suggest just riding your bike as it is now and try to relax and enjoy the ride