1 month is not exactly 4 weeks. There is typically 30-31 days in a month. Which is 4.3 weeks. If that was the case, you'd be pregnant for 10 months...

Why is there a formula for counting mnths? 4 weeks= 1 mnth, 18 weeks is 4 mnths n 2 weeks. I am 19 weeks which means I am 4 mnths n 3 weeks. Next Saturday i will be 20 weeks which makes me 5 mnths. I jus dont get how counting mnths is different whn ur pregnant. Why is there a new formula for counting weeks?

beginning of it yes