Working out the due date

I know that the deed was was 2nd or 3rd of April, so fertilisation was any 5 days after that right?

Cant see a doctor till the 11th but apps (from my last period) have predicted i fertlised the egg the 8th and implantation the 15th?

My prediction is thats wrong so could i be further ahead?

It says im 4 weeks. My test said 2-3