First pregnancy and 4 weeks pregnant!

Hi everyone! I’m 32 and newly pregnant with our first and I have so many questions! We are about 4 weeks..I think. But I’m not sure how to really tell. The start of my last period was 11/11.

When do you typically go see your doctor for the first time? I called yesterday and they said typically 8 weeks?

Is there anything I should avoid? Is sex ok to continue? I imagine it is but I just want to make sure.

What about food? I know coffee over 12 oz and no alcohol obviously but is there anything else that could put our baby at risk?

What about vitamins? I have been taking them for a few months but is there a brand that is best? And is it ok to take a multi vitamin too?

Thank you! Any advice is appreciated!