Extreme Constipation

Hello, does anyone have any suggestions for a 1 year old (13mnths) with heavy constipation. It has been extremely hard balls that she screams and struggles to pass. Now nothing. She squeezes tight to cancel out the urge and wont go. Anything to make it super soft almost watery without it having a negative side effect? I just need all this poop out. We've changed the diet bt we cant see the effects of it because she wont let go of the hard stuff that's in the way. Help! Any suggestions are appreciated.