Calculating how many weeks

Amy

I'm very confused as to how far gone I am lol.. my last period was the 25th match, but I did not remove my coil until the 11th April ( so I can't of fallen until then).. I had a positive test on the 23rd may saying 1-2 clear blue ( so I'm around 4 I would guess?) but what is confusing me is there dating me from my last period .. but obviously I wasn't pregnant then lol.. so

Do I go by the 11 April when I removed the coil?.. nhs said yes but midwives said it would be my last period help please :)