im 5'8 im a sinker ball pitcher that bearly allows a ball go past the infield.....but hitters in my high school league are started to wait back on my sinker..so is there anyway i can speed it up making it faster?

Generally, speed comes from the legs - up. That doesn't mean strengthing your arm and shoulder won't help. Light weight training to stretch your arm and back while toning the muscles, along with endurance and strength building of your legs will pay off in the Spring. Of course, start off slow and take it easy so you don't hurt yourself and build up carefully. You have all winter and you don't need to be Mr. Universe!

Strengthen your legs. You'll get more mileage out of that.

The best way to improve pitching is to gain strength in your legs. Pitchers get most speed from their legs

Do something to get more strength in your legs.

If you ask a major leaguer they will tell you the best way to build arm strength is to throw long. You want to start out short of course and work your way back until you are throwing the ball as far as you can with the path of the ball resembling the curve of a banana.

Also make sure that you work on your mechanics on the mound. A lot of theories out there but look at the stuff that talks about rotational pitching (or hitting) as people dig deeper into mechanics torque is recognized as the key to power in baseball.

1. Long Toss
2. Leg Strength
3. Whole body flexability
4. Core strength

In order of importance.

The guy above has the right idea. The one thing I would like to add is gain your strength by staying away from weights. Instead of weights use elastic bands of strong resistence. This will accomplish the same thing as weights but avoids damaging your body as much as weights do. Also, throwing using a slightly weighted ball will also add some velocity, it's sort of like the effect of running with ankle weights.