What will I feel under IV sedation for a BBL? Will their be any chance I will feel pain or will I be numb?

I use IV sedation prior the epidural for my procedures. 
The IV sedation will put you to sleep deep and profund,  and will not feel anything, not even the epidural injection.
Is less risky for the patient that the General Anesthesia, so less risks is always the best option.

There are some grey areas where IV sedation and general anesthesia overlap. IV sedation can be very light where folks remember their procedure, or it can be heavy, where you are completely asleep. Your airway is much better protected under general anesthesia and I believe, when you are laying face down (such as during BBL), general anesthesia with a protected airway is safer. Make sure you are having surgery in a state certified facility and with and American Board of Plastic Surgery certified surgeon.