Hi Hallie, Welcome to HealthcareMagic Forum.
It is a Serious Misconception. Kindly don't believe in such Rumors. Exposure to mice, rats or any other mammal will not have any effect on the Human Hormones including HCG
To increase the chances of conception have alternate day Unprotected sex between the 10th and 20th day of your Cycle. Eat healthy nutritious balanced diet which should include fresh fruits and green leafy vegetables and maintain a Healthy weight. To test for Pregnancy
wait for a week after you miss your Expected periods and then test using a Early morning Urine sample.
Good Luck, Take Care.