Hugs to you - we all fail at this parenting lark, and usually keep on failing until our offspring have children of their own.

While you're probably not in a headspace to do this, what with being towards the end of pregnancy, but is it worth trying natural consequences rather than time out? Your DD has to help clean up the mess she makes. I find I get grumpier cleaning up others' mess so I need help or I get all shouty and mean. I liked doing lots of outdoors time with Liebs as the mess didn't matter so much then - at least until DH changed the back gate so it could be opened easily!