What are the chances of getting pregnant if two weeks after your period you deposit your boyfriend's semen into your vagina?

The implication of your question is unethical, indeed, even sinister. Having said that, if you managed somehow to collect your boyfriend's semen (perhaps in a non-spermicidal condom) and refrigerated it to preserve the sperm's viability and then managed to inject it (a sterile turkey baster?), it is possible that you impregnated yourself. Nice going. Deposit? Hmm...Don't do it please! You will regret doing it. Two weeks after your period is the MOST fertile time. A baby is there forever! You are probably young so you should NOT commit yourself yet, although it is non of my business. To answer your question: sperm dies soon when exposed to air. If you collect it and your boyfriend finds it he will probably be angry so you may lose him. You may lose him if you impregnante yourself because he can get very scared and "run away". Chances are very high for a possible pregnancy in mid cycle. Pregnancy should be a pleasant period in your life so don't take the chance.