best advice is to bd every second day, not every day. Chart cm and record your temps, if you need more cm, drink green tea, robitussin cough micture and graoefruit juice are all good remedies, or get some pre-seed lubricant. Ensure that you know exactly when you O and have had sex 12-24 hours before O. It takes sperm 12 hours to be ready for the egg so they need to be there waiting in nice fertile cm. OPK's will detect your LH surge which says you are gearing up to O which can be anywhere from 12-48 hours after surge is detected and the ony way to confirm you have actually O'd is for your temp to jump and sustain that rise for at least 3 days.
Even with all the above in place the most fertile couple on the planet have about a 20% chance each cycle!!
Check out the Great Sperm Race Documentary it will blow your mind