I just took my first white pill of lo loesterin fe and I’m so nervous that I don’t get my period 🙈

It's actually very normal for bleeds to lighten or to not bleed at all on that pill (or any pill.) One of the ways birth control works is to thin your endometrial lining. As long as you take your pills correctly there's nothing to be worried about.

Ok I did have sex on the first week of pills but I took a plan b

make sure you test for pregnancy three weeks from that date

Ok! I think I’m in the third week I beleive

If you had sex when you weren’t protected yet you will still need to take a test 21 days after using the plan B, as plan B is not guaranteed to work.