There's no research or clinical evidence to support that "worrying" hinders conception. Extreme stress can affect your ability to ovulate in very rare cases. "Worrying about it," on the other hand, can be useful if it moves you to action in the form of determining your ovulation and then timing intercourse to coincide with your most fertile time.
Frequency of sex around ovulation is important and I advise my patients to have sex at least every other day during this time. I stress, unless you're ovulating, you won't get pregnant. According to the New England Journal of Medicine, a major study found no difference in pregnancy rates between couples who had sex daily and those who had sex every other day.
It is thought that sperm with Y chromosomes (male) swim faster than sperm with the X chromosomes (female), and are able to reach the egg earlier in its journey to the uterus (i.e., right after ovulation). Although it sounds believable, a New England Journal of Medicine study found nothing conclusive to this theory.1
Actually, some studies claim that a man's sperm count may be higher in the morning. Furthermore, having sex with the man on top is recommended. The missionary position allows for the deepest penetration, placing sperm closer to the opening of the cervix, which will allow easier access to the egg.