sight reading is a skill that needs to be develope...it takes time...
doing scales( other workouts ), rhythmic exercises help with sight reading because you will get familiar with the rhythm, syncopation...
i developed my sight reading by playing hundreds of flute scores ( it helped for drums too )once when i was in an outside band...it really trains your mind!
so..try out more stuff...once u get the hang of it...go back to old ones...you would be surprised at your sight reading standard...
PS: if u cant do it fast...take it slow...and...SUB DIVIDE! :lol: good luck!