A typical starting pitcher will make 6 starts a month, and pitch an average of 6 innings. You may want to use 7 innings as the average start in fantasy leagues, because when you have higher quality pitchers they tend to go more innings. That means that you can count on about 42 innings per month, or 84 innings for the rest of the year from each of your starters. For closers, an average closer throws around 90 innings per year, which works out to 15 per month, or 30 innings for the rest of the year.
So, you just need to work out how many innings will be used by the pitchers you have and look at trading some starting pitchers away if you are going to go way over.