So my husband has a 4 year old daughter from his previous marriage, i have a 5 year old from mine, and together we have twin girls. We really want to try for a boy. From what i have learned the time of intercourse as close to ovulation as possible is favourable for a boy as male sperm swims faster. My question is: how does ovulation tests work, when you get a positive, how long after that does ovulation actually occur. Or can that not be determined definitely?