Best advice I can give is to find a pitching coach and pay for a lesson or two.
We are going through this process with my '07 son. Much like you, he is a Junior, 6'0", 225 lbs., LHP. He has had success as a pitcher, but both of us felt that there were some fundamental problems that were limiting him.
We have to travel 4 hours one-way to meet with a pitching coach. In the first lesson, he identified 3 or 4 things (minor things) that had a cumulative effect in reducing his velocity. Son has started working on drills to address those specific issues.
Worth the money and the drive, absolutely if it helps move him toward his dream of playing in college.
In your area, it will probably be much easier to locate someone who is qualified and competent. I want to stress competence. If you can find someone competent, it will be well worth the dollars invested.
Good luck!