my transmission will only work in reverse

i drove the car home with no problems or noises although the transmission did jump out of drive and then back in about a month ago but no problems with transmission since that time but today after parking my car i went back outside to leave and after backing out of my drive way it would not go into drive low 1 or low 2 it only went into reverse i was wondering if the transmission went out or could it be a filter or a sensor lost and i have no idea what to do with it