Boxer training Regression! Please Help!?

My Boxer pup is 8 months and has been fully potty trained since 4 to 5 months. she is now regressing and has had almost 10 accidents this week! I have been taking her out every hour and as soon as I walk back into the house she goes to the bathroom! I am so frustrated and don't know what to do! I feel like she needs a punishment to know that she is doing wrong because yelling at her is doing nothing! She use to be such a good girl and now is going backwards! Please Help!