Hi there im not sure about the birth control.i can tell you though that short periods is perfectly normal.i have gone from a normal 4 day cycle to a 24-36 hour cyle,i was concerned this wasnt normal.but it is,i also concieved with periods this way...im 34 they say once you are in your 30's takes a little longer,but hang in there.it will happen...
Your cycle is the time between periods. So by cycle you mean that your *period* is lasting a shorter and shorter amount of time? If that is the case, YES it is normal! You can have a period for ONE day and it's still normal.