It is, indeed a form of oxalis. This site won't let me post the site linking to Dave's Garden, say it will spam. But you can look for "pink wood sorrel" and find it there.

Probably Oxalis debilis (Pink woodsorrel), an Introduced species. Link below.
Most of the native species are yellow-flowered, but a few are violet-blue or near-red.

Here is a link that might be useful: Pink Woodsorrel