I would suggest you do some light reading about plyometrics and add a plyometric workout to your existing workout. They don't generally take that long and can be done in conjunction with other things but yet the benefits can be pretty substantial for increasing your speed and power without adding bulk and weight to your frame.
I have attached a web site to help get you started with this that will also give you some workouts for increasing your punching speed. You should see results in as little as 2-3 weeks. Enjoy.
http://www.sport-fitness-advisor.com/ply...
I could give you a massive essay, but here's an article that is better than any answer I can give you.
http://www.myboxingcoach.com/improve-pun...
buy a speed bag to in crease your speed
What exercises can increase punching speed?
