I'm not having any sexual fulfillment from my boy friend after giving birth. Why not?

Lots of reasons. This really depends on several factors: how postpartum are you, beastfeeding, fatigued, and your relationship with your partner. Also, simply being concerned about your baby may interfere with sex. Delivery also causes changes to your body/vaginal area that may make it less sensitive to sex. Rest assurred that these symptoms are not that uncommon after delivery. Talk with your partner.