sharp pelvic-like pain while having intercourse?

[dNiC0LE92]

i was having sex with my bf (with protection) and when he bent me over and he started "doing it" i felt a sharp pain it felt like i was losing my v-card all over again. but when i laid on my stomach and we went at it i didn't feel anything. could it be from sitting without back support for 6 hrs then a another 1 1/2 drive home, or is it something different. Also we did it the night before and no problems. SORRRY FOR THE DETAILS