I'm supposed to start trinessa today but haven't got my period yet its my first month,what do I do?

Were you specifically told this Sunday or the Sunday after your period starts? When you start them you just keep taking one pack after the other, including the inactive pills. Once you're on the pill, when you take them has nothing to do with bleeding, so if you take the inactive pills and don't get a period, you still start the next pack at the time you should. If you don't start your period today, you can wait to start the pill until the first day of your period and go from there. You just start with the pill for that day and follow with the 28 pills. Just remember to use back up birth control for at least the first 7 days of pill start.

You really should wait until you get your period. It works better this way and you will have a much smoother time adjusting to the hormones if you wait for your period. When you start, you start with the first active pill either the first day of your cycle or the first Sunday after you start (if you prefer to be a Sunday starter). You should use back ups like condoms for the first seven days. If you start midmonth (not recommended) use back up for the entire first cycle (whole first pack)