Got a single canker sore from nowhere, had sex recently and could also now be pregnant, read that canker sores = folic acid deficiency super worried, could this mean ive already harmed the baby?

These sores do not always mean a folic acid deficiency. If you take a prenatal vitamin every day, you will get plenty of folic acid. Folic acid is found in many foods so if you eat a balanced diet, you are unlikely to be deficient in folic acid. You can also ask your doctor to check a level so that you can decrease your anxiety. Do a home pregnancy test to confirm that you are pregnant as well.