It is quite normal and all guys experience a refractory period (also known as the recuperation period) immediately following an orgasm, during which time they are unable to achieve another erection, and a longer period again before they are capable of achieving another ejaculation. Quote (read the full text here): "The duration of the refractory period varies considerably, even for a given individual. Age affects the recovery time, with younger men typically recovering faster than older men, though not universally so. Some men are able to achieve sufficient sexual arousal immediately after ejaculation, and others may have refractory periods of less than 15 minutes. A short recovery period may allow them to seamlessly continue sexual play from one ejaculation to sexual stimulation in preparation for the next. However, other men are averse to stimulation during the early part of the refractory period."
A quote from another entry reads: "According to some studies, 18-year-old males have a refractory period of about 15 minutes, while those in their 70s take about 20 hours, with the average for all men being about a half-hour. Although rarer, some males exhibit no refractory period or a refractory period lasting less than 10 seconds" and "refractory periods range from human to human, with some being immediate (no refractory) and some being as long as 12 to 24 hours."
Be grateful your b/f does not have a refractory period lasting less than 10 seconds....