how to calculate how pregnant????confused!!!!!

[supadupapupascupa]

My first day of last period was friday 15th April. I understand how the weeks work but not the days. My doctor said 4+3 on the 16th May but I don't see how?

Does anyone know?

Week 1 Fri 15/04 to Thu 21/04
Week 2 Fri 22/04 to Thu 28/04
Week 3 Fri 29/04 to Thu 05/05
Week 4 Fri 06/05 to Thu 12/05
Week 5 Fri 13/05 to Thu 19/05

I understand that during week 5 you are 4 weeks pregnant, but how do you count the days? Is Friday day 1 or day 0?
I thought that on the monday 16th i was 4+4?

I know it doesn't matter, and believe it or not This is my second so I should know. But it's driving me a bit nuts not knowing.

The day your period starts is day one of week one. Cycles are assumed to be 28-days long (although this may not be the case for you, but when it comes to talking about your pregnancy a 28-day cycle is the default). So on day 28 of your cycle you're considered to be 4 weeks pregnant. So on Day 29 of your cycle you would be 4 weeks + 1 day. Now, this can be adjusted by a dating scan (and often is), but for arguments sakes in the early days of your pregnancy that's how your doctor would calculate your EDD.

a-ha! so monday would have been 4+4

Thank you, I thought it was just me being daft!