testing 40+ days after

I am on nexplanon, never gotten pregnant. I took a test 40 days after intercourse as I have been testing since 7 days after. It is now 43 days after. I only have 2 tests left and I've used 40+ tests during this time... Can I trust the negative I got 40 days after? I used night urine. I do know the facts but cryptic pregnancy scares me alot.