Oral sex does not affect conceiving. You need to ensure your having sex during your fertile days to increase your chances of getting pregnant. If you've been trying for a year and no luck the it might be worth a trip to the doctor fir some tests, a sperm test is a good place to start.
Hello,
Every man has sufficient sperm count and oral sex cannot kill sperms. You can try conceiving during ovulation days for maximizing the chances of conceiving. There are many vitamins which can help in ovulation like vitamin D, C, B6.Iron balances ovulation. Get a prenatal checkup done and ask your doctor about prenatal vitamins like folic acid. Take a healthy nutritious diet and adequate rest. Stay away from stress and exercise daily. If you do not conceive in next few months you and your partner may need evaluation for infertility. Hope it helps. Best wishes and regards!