How soon to test for pregnancy

Mistakenly deleted my post 🤦🏾‍♀️🤷🏾‍♀️ I hear women say they are 3 weeks pregnant..how do you find out that early??? What test do you use???

I think I’m pregnant, because my 2 year old keeps asking to talk to the baby. She lifts my shirt and begins talking and rubbing. It made me think of all my weird cravings and symptoms these last two weeks...fatigue ( hubby too), hot wings and crabmeat, terrible lower back pain, weird taste/dry mouth at night, and nausea out of this world. If I go by my last period I’m exactly 4 weeks, but my cycles are 35 days apart next set to arrive the 21st.

What test would let me know this early and when should I take it?