A lot of good info has already been sead but it sounds like maby you need to see a proshop and get that bow tuned before you even think of broadheads[&:](imo)

Then practice, practice, practice. And strive for the best shot placement within your effective range.
Like mobow sead! If your arrrows are fish tailing don`t try to cover it up by using mech heads. "First get that bow tuned"!
Then lets talk broadheads.