If you find them uncomfortable, you might want try to scheduling for a time a few days after your period ends. Your breasts will tend to be more tender right before your period or around ovulation, especially if you have fibrocystic changes. This may help with visibility on the scans a little, too, as your breast tissue may appear less dense at that time.
Another option, if you have dense tissue, is to ask to an ultrasound instead of a mammogram. These are not painful at all, but do have some limitations in terms of what can be seen on them and, if you live in the US, may be something you have to pay for rather than being considered preventative care that will be covered in full by insurance.