Does it hurt straight away or like after your second set of doing them?, one alternative would be to do it with a weighted vest and do less reps...or it could be that you are leaning too far forward thats what i use to do and i had serious pains in my shoulders i actually recorded myself doing them and realised how wrongly i was doing them... or maybe you are going to low and putting strain on your shoulders get a mirror or record yourself to see your form man.
Hope i helped at all! :)
Pain is temporary. It may last a minute, or an hour, or a day, or a year, but eventually it will subside and something else will take its place. If I quit, however, it lasts forever.” - Lance Armstrong.