12day late period, lower back and abd pain, nausea, neg hpt, headache, fatigue, unprotected sex 1week after nuvaring removal, lmp jan 1. im cofused?

Late period common: It is very common for there to be a delay in the resumption of normal cycles after stopping birth control. This may also be associated with different hormonal symptoms than you are used to. If the hpt is negative, then that means you didn't conceive from intercourse that took place more than 2 weeks ago. (if you had sex more recently than that, it may be too early for the test.).