How long does it take to schedule an appointment at NUH via referral letter from polyclinic?

Im currently at 8 weeks pregnant and I am worried I will miss the chance to do some tests that can only be done during 1st trimester. Have not gone for any pre-natal appointment as I only found out I am pregnant at 7 weeks. This is my first time being pregnant after trying for 4 years and I am worried if pregnancy is viable or not. I have been consuming over the counter folic acid from watsons, 500mg + 800mg, is that too much? Thank you!