Help please missed period

Hey girls. June I took plan b and that month I had two periods. July I had my period normally w safe sex but mid August my BF came

In me and ever since then I missed my

Pwriod. Took several test w diff brands but negative. No symptoms or anything until this week and last week. I felt nauseous and bloated.. Should I be worried? What do

You ladies think?? Anyone relate? Please help