Hello, and I hope I can help you today. Condoms are really only recommended for single use, because they are rarely washed, dried, and re-examined for holes for using the second time. However if your boyfriend never lost his erection, which might cause leakage around the base of the condom, it is likely that you still would have been protected; a second ejaculation within a short period of time is unlikely to have as many sperm in it as the first one. I would suggest, just to be safe, that you consider using emergency contraception, commonly referred to as the morning after pill. It can be purchased in a drugstore without a prescription and when taken within 72 hours of unprotected intercourse it is greater 90% effective in preventing pregnancy. The medication is safe and if you strongly do not desire pregnancy, I would advise you to look into it. In the meantime, I would advise your boyfriend never again to reuse a condom, for exactly the reason you described. I hope that I was adequately able to answer your question today, and that my advice was helpful. Best wishes, Dr. Brown