Shih Tzu housebreaking regression

Question
Pebbles is 15 mos old.  She is spayed and is mostly inside.  She is a calm and very well behaved dog.  I was never a dog person and never wanted a dog but my 3 kids talked me into it and it's the best decision we ever made.  WE all love her so much and can't imagine getting rid of her for peeing problems.
I did crate train her right away and she never had accidents in her crate.  Then I gated our kitchen which lead to a doggie door so she could learn to go outside on her own.  And she did.  Then she had free access to the house only when we were home and she would go outside but in the last month she is just peeing and pooping where ever she wants.  I don't think I ever had her 100% potty trained but I would say I was very close and now she seems worse.  She will go outside when we walk with her outside and we say "go potty" and she will.  But if we don't take her she will go in the house.  I also have another doggie door that will go outside our garage so she has 2 ways to go outside at all times and she seems to choose too just do what is conventient which is to go inside.  I love this breed of dogs but I don't seem to understand her.  Can you help??  Also what do I do when she has an accident.  We don't scold her. We just say...you need to potty outside and we put her outside and shut the door for a few minutes.   Please help!!  Thank you so much.

Answer
When you catch her in the act of going potty in the house, you should make a sudden, loud noise to startle her (which should make her stop going potty). Then, encourage her to follow you towards the doggie door and go out. Go out with her (not through the doggie door of course *laugh*) and praise her when she finishes going potty outside. Then just clean up where she went in the house with no more scolding. If you just happen to find a spot where she's gone, do not scold then, because she will not understand why she's being scolded.

If she's going potty in the house while you're away, then you may want to consider crating her again, or confining her to only a small area near the doggie door, so she basically has two choices - be inside in a small area or outside. This will make her less likely to want to 'go' inside.

When you're home, let her drag a leash and/or keep her confined to the room you're in so you can keep an eye on her and get her out as soon as you see her starting to circle or sniff.