I don't understand the bar

Okay so i have the bar implant and my boyfriend uses condoms every time we have sex what are my chances of getting pregnant I've had the bar for 4 months and eve is saying my period is 14 days late I already took a test last Friday and it was negative but I'm still freaking out about it and trying to remember if we ever did it last month without a condom am I crazy or could I be pregnant