5-6 days late but still not pregnant

So we started liquid Geritol in October on CD 2. I do not use opk’s because they’re hard to read and I’m forgetful. However we used Geritol and finished one bottle, started the other but we haven’t drunk much out of it (probably 2 or 3 days on the new bottle). My period is 5-6 days late and I took a digital last night and it read I’m not pregnant, I do not recall being this late since last year August. I’m so lost and sad right now.

My question is:

Has anyone got a late period when using Geritol?

What’s a good test to take? (The one I used was a Kroger brand)

When should I go to the doctor?