my ex has full custody of our daught can i keep her over night on weekends?

If you do not have a court order saying you are entitled to overnight visits then the answer would likely be no.  If you have an order stating that you are entitled to parenting time, pursuant to the Indiana Parenting Time Guidelines, you may find that your daughter is still a bit young in terms of an alternating weekend schedule, unless you have been previously exercising parenting time for a lengthy period of time.