My pitching repertoire?

Last year I was the closer for the Freshman baseball team. We had tremendous success ( 18-2 I think), And I had the same kind of personal success (Sub 1 ERA and WHIP).

My success was largely due to only pitching for an inning or two, because I only threw a fastball and a bad, slow curveball.

For every 10 pitches I'd probably only throw 1 curve. (It was terrible, but I needed a change of pace pitch).

The reason why I was so successful was that I have Pin-Point accuracy ( 2 walks in more then 30 innings). And that my fastball was much faster then everybody elses.

Basically, I wen the entire year pitching lights-out with oinly a fastball. It's near impossible to do that in High School and it IS impossible to do that on JV/Varsity. I developed a great slider with great command with it.

My question is, should I add one more pitch? I've been trying change-ups and curves for a while but they are not good quality pitches for me. I can throw a forkball inconsistantly with great movement when I throw a good one, but I can never find a way to make it consistant.

So is fastball slider all I need as a reliever on varsity? I thought it'd be, but if it is not, then I'd like to start the developemnt now.

Thank you