Do you think adding a phone spy to my husband's phone will help?

Recently i found out my husband has been talking and texting his ex. He also put a protective password on his phone. i am thinking of buying the cellphone software to find out the truth. Am i going to need his phone to spy of since we are on the same account i can just use it without even needing anything else? I am tired of wasting my time on a man that cheats and i want to know the truth now.