What is the chance of pregnancy on day 7 of a cycle that lasts 33-35 days with using a condom during the last half of intercource?

Plan B. Condoms are designed to be used from start to finish--not just at the end of intercourse. This is because about 4-5 million sperm are released in preejaculatory fluid. Use over the counter Plan B if intercourse was within 72 hours to decrease the risk of unplanned pregnancy.