if you have back pain you need to learn how to stabilise your spine . One of the hall marks of good stabilisation is the ability to both contract the abdominal wall and breath at the same time. Poor spine stabilisers, in effect, switch between bracing their spines or breathing. In short can you brace your abs ( not suck in!!) and continue to breath?
If not,  train yourself to breath freely while maintaining an isometric  contraction in the abdominal wall.