Pregnant at 15?!

Me and my boyfriend have been together for a long time, and we've always used protection during sex. 
I'm 15.
He has never cummed inside me and he always checks the condom after he ejaculates to make sure it's not ripped. 
My period is one day late.
What do I do😭It's been late before by one day and I was fine, and I know someone will probably say "you needed to think about this before you had sex, you're clearly not ready", but I am. We've had sex lots of times and always been safe. My boyfriend says that worrying will delay it even more, and he is reassuring me that it's fine and it's VERY unlikely. 
BUT WHAT IF I AM PREGNANT?!
What happens then😭Please, anyone give me advice and reassurance, thankyou.