No sex allowed before FET

I asked my nurse if we can have unprotected sex the night before modified natural FET as there’s a study showing that exposure to sperm increases implantation and pregnancy rate. But my nurse says we can’t have sex because it could cause twins.

But the night before FET would be 5 days after hcg trigger/Lh surge which should be way past ovulation. I’ve also read there’s a risk of infection but I’m on a 5 day course of antibiotics before FET.

I read a bunch of stories here of people having successful FET after having unprotected sex the night before and failed if no sex so it’s really tempting me. What do you think? Has anyone had successful FET without sex prior?

Our last modified natural FET failed, didn’t implant at all. Didn’t have sex the whole month prior to FET.