Im on birth control missed my last period 2 weeks later had spotting 1day for maybe an hr then week later have spotting again.what could cause this?

If taking the pill: Correctly it's not uncommon to miss a period. It's also not uncommon to have some spotting. There are other things that can cause both like pregnancy if u haven't taken them correctly or a cervical infection for the spotting if you have a risk for getting a cervical infection. Your likely fine and it's a nuance of being on the pill, check a upt if concerned. Gd luc.