Taken from babycentre
Can having too much sex affect our chances of getting pregnant?
Anna McGrail answers:
No. While many couples believe they have to 'save' the man's sperm until the exact moment of ovulation, that's not true.
It is a myth to think you should have less sex in order to conceive. All the real evidence shows that the more you have sex, the better your chances of getting pregnant. In fact, having sex often ensures that the sperm in a man's ejaculate is as healthy as it can be. While it's true that the density of sperm in each ejaculate diminishes with frequent orgasms, all that really matters is that there is some sperm in the woman's Fallopian tubes during the time of ovulation.
This is not to say that you should have or need to have sex every day when trying to conceive. Sexual intercourse every two to three days throughout the month is most likely to result in pregnancy.