Previously House Trained Dog Peeing and Pooping Inside?

I have a three year old Shih Tzu, who is potty trained with full access to the backyard all day. It has been over a couple of months since she started to pee and poo around the house. At first the accidents would happen when we would leave her door closed or when it would be raining, and she would do only on the carpet. This week, she began going on the tile, that she has never done before. I don't know what is going on with her, sometimes I think she needs to be reminded of who is the boss.

Another thing is that I am pregnant, and I wonder if she senses that and somehow is reacting to the soon to be here new member of the pack.
Please help. I'm thinking about going back to square one of the training with her, leaving her crated while at work, giving some tough love, etc. Am I on the right path?

By Roberta from Austin, TX