Feel sick this month but i have the Nexplanon 😐

So i got it last year in june. After i had my 2nd baby on March last year .. this month my period hasnt came yet.. i been sick lately like alittle nauseous.. and tired.. but i cant be pregnant because my doctor said i cant get pregnant on the birth control .. me and my partner dont use any protection as my doctor said its okay to not use any protection… but i was just wondering can u still get pregnant on this birth control if so can i sue lol… if i am.. im scared now i read that all birth control isnt 100 fully percent effective.. 😨😨😨😨😨