I used to work out 4month aso and now I started again but everytime I do crunches I get back pain amd chest pain is this normal...It hurts whenibreath?

NO!! It is never normal to have pain while exercising. If you are having "chest" pain it would be best to get evaluated immediately. For your back pain it may have more to do with technique. I would get with a licensed physical therapist or trainer and have them help you.
Chest pain. If you are having chest and back pain consistently you need to get checked, you may have heart problems/ or. Disc problems to account for your back pain.