How likely is it that I will conceive if I had sex during my period & about 2 days after it ended; he ejaculated multiple times, I have a 28 day cycle?

Unlikely. Remember you are not fertile during menstruation. You are fertile during ovulation. Ovulation is when the ovary releases the egg. Sperm left in the vagina on any of the five days BEFORE ovulation are the sperm most likely to cause pregnancy.