need clarification

Shiniqwa.
My first day of my last cycle was may 15th. So that would put me at exactly 4weeks and 3 days pregnant. If I base it off my last day of my cycle which is the 20th of may. I'll be on 2 weeks. Which do I go by the first day of the last? I need some understanding 

Glow Resources

Let’s Glow

Glow is here for you on your path to pregnancy

Glow helps you navigate your fertility journey with smart tools, personalized insights, and guidance from medical experts who understand what matters most.

25+ million

Users

4.8 stars

200k+ app ratings

20+

Medical advisors