[Erika]

5lbs is too high a jump to do without working up to it. You should put a theraband on the bow with your old limbs and do some work for a few weeks at an in between weight.

There is NO reason why 45lbs should give you shoulder pain unless your technique is bad or you have a pre-existing injury.

Make sure that you are not trying to set your shoulder under load. ie don't move it after drawing the initial few inches. Also check that your shoulder is in correct line. ie when you are aimed at the target your shoulder line should be aimed to the right (assuming you are right handed).