Chances are,you are not pregnant.It is recommended to use backup when switching pills,but if you have been on bcp's a while and are faithful in taking them,you are probably not preg.If you are late in getting your period,then take a preg. Test.It does seem like overkill to use a backup when you are on the pill,but,if you want to be absolutely certain,use one.That is the whole point of contraception,afterall,right!!!????Good luck to you.Patty