This is something that always bothers me. Swearing with God's name is not using the lord's name in vain. Using God to fulfill personal desires or make false oaths is what that commandment addresses. It's right in the words, vain, referring to vanity.

"God told me you need to have sex with me to save your soul." = Not Ok

"I swear to God I'll pay you back." then don't pay back = Not Ok

"God damnit!" = Ok