husband and I had sex at 6 weeks pp...no condom, he pulled out

I'm scheduled to get the implant on the arm this coming Wednesday

QUESTION: IS IT POSSIBLE TO BE PREGNANT; GET A NEGATIVE TEST AND ONCE I HAVE THE EMPLANON BECOME PREGNANT ORIGINALLY FROM THAT FIRST TIME AFTER THE 6 WEEKS????? JUST ASKING SINCE I IMAGINE THEY TEST YOUR URINE BEFORE GETTING THE PROCEDURE DONE? I HOPE.

AND IM WORRIED because my MIL told my husband she had a dream we were having twins and EVERY time she has a dream about me having a child if becomes true...I Just had a baby shes a month old and I do t want anymore kiddos!! ID DIE...