On work days I eat at 5 am and workout at work for 20 minutes at 8:30 am and have lunch at 12 pm.
I am getting stronger I have gone from 4 pullups to 25.
But my muscles don't seem to grow much.
Should I eat something right after the workout? Or do something else?
Strength is very strongly correlated to muscle size, it's just a slow process. Keep getting stronger and you'll get bigger.
You also need surplus calories to optimally build muscle... so once you're lean, you might want to add a little extra protein and post workout carbs (taters, fruit, rice) to up your calories and maximize recovery.
Lastly, doing a combination of strength work and higher volume training is generally regarded as best when hypertrophy is your goal. Give [URL="http://www.kentmccannfitness.com/2012/09/23/everything-about-building-muscle/"]this[/URL] article a read for a bit more on muscle growth if you're interested in the science behind it!
Out of curiosity, just how closely is strength correlated to muscle size? My muscles seem to be growing much faster than my strength is, and I train for pure strength, not hypertrophy. Of course, I'm still pretty new to the barbell - maybe it has to do with neuromuscular adaptations at this point? I dunno...i'll take it, though...