How effective is plan B after 3 days?

The Little Mermaid
I had unprotected sex and been wanting to TTC but my fiancé is now telling me that he's worried that he got me pregnant and to take plan B because he isn't ready to be a father. However, I am ready to be a mother so I don't think it's fair that he's making me take plan B if he ejaculated in me and knows the consequences. There is some miscommunication on this topic but he ejaculated in me and I'm not on any bc right now. We did it on Sunday and now it's Wednesday. Just last night he's telling me that he's worried and he's not ready for a family yet. He wants to wait another year because he wants to travel a bit, buy a home, etc. Buf I honestly don't think there is a perfect time to have a baby. Anytime is a perfect time. Children are blessings!
But now I don't know how effective plan B is today. According to Glow my chances of getting pregnant on Sunday was 6% ... I don't really go by any apps for fertility because our bodies are different and each day is different. I only use the calandar to track periods.