What Causes Tightness In The Vagina During The First Intercourse?

i got married 3 months ago. my wife and i spent 3 wks together b4 she had to travel abroad. but i had difficulty disvirgining her. the vagin was too tight and whenever i attempted entry, she would cry with pain.at other times, my penis would simply slip out of her vagina entrance,i will meet her soon. how can i disvirgin her with ease?