Missed my period two months in a row, on birth control and the pregnancy tests are negative. also only spot one day on placebo pills, is this normal?

Yes: In general birth control pills are dominated by progesterone which thins out the uterine lining. that is a good thing. some women when they take the pills will stop having periods as their lining stays thin all the time. it is not medically a problem

Sometimes, yes: As long as this is a transient, as opposed to recurrent, occurrence (more than 5 cycles). This can especially become an issue with ocp (oral contraceptive pill) transitioning.