TLDR: use an ovulation test. I love Clear Blue digital. Taking your temperature is free but spending money on these tests is so much more effective.
Tracking fertility days: There are basically 4 days a month you can have sex and make a baby as a result (and if you have sex in that window, there’s a roughly 30% chance of conception). I feel very mislead by 8th grade health class, but I digress..
Fertilization happens on the day you ovulate (which happens 1 day a month) however, sperm can live in your fallopian tubes for up to 4 days (that’s we say there’s about a 4 day window that you can get pregnant). For the greatest chance of fertilization, the idea is to have the sperm waiting for the egg BEFORE it releases so it can engage in a sneak attack on the egg as it travels down the fallopian tube (See: Sun Tzu: the art of war). Typically, ovulation occurs in the middle of our cycle (Day 14 of 28, in theory) but every body and every cycle varies, some ovulate day 10 and others on 20 so the best way to know for sure when it’s time to try is a combination of tracking your cycle and taking ovulation tests.
Ovulation tests work just like a pregnancy test, it just tests for a different hormone. Pregnancy tests identify if there’s HcG in your urine, which is a hormone that’s released only when you’re pregnant (note: this hormone increases gradually as a pregnancy progresses and at home tests need a high enough concentration to identify it… which is why they recommend waiting 2 weeks to test). Ovulation tests test for LH, or luteinizing hormone, which is a hormone that’s released 24-48 hours prior to ovulation (this hormone signals to the body to release the egg). There is also an increase in estrogen leading up to your ovulation window as well.
This is why I love Clear Blue Digital Ovulation Tests. They test for both LH & Estrogen and so they can typically identify 4 or more fertile days, giving more opportunities / greater chances of conception vs. narrowing it down to a 24 hour window. They show your “high fertility days” (a blinking smiley face) and “peak fertility days” (a solid smiley face) to give you better insight into what you’re working with.
A lot of people talk about taking your temperature (your basal body temperature, or BBT, spikes AFTER you’ve ovulated). The idea is if you consistently track and chart your daily BBT, you can identify and predict when you will ovulate. I have two issues with this method– the first is many things can effect our BBT, like drinking alcohol or being sick. The second issue I see is you may not ovulate the same day every cycle… so tracking your temperature can give you insight into when you’ll likely ovulate and confirm after you did, but only an ovulation test can truly confirm the process is in motion and ensure you don’t miss your window.
Lastly, to note: You can time it right, the sperm can fertilize the egg, it can travel to the uterus, and it just might not implant in the uterine wall. If it doesn’t happen it doesn’t mean you’ve done anything wrong. The goal with officially “trying” is to increase our odds, but if we don’t succeed it is not because we have failed or done anything wrong.