I've had anal sex (without protection) a few times and my period is late, pregnant?

Ok. Before anybody starts I know I was stupid.

 I'm 14 years old and my boyfriend and I have been going out for nearly a year and a half. We've had anal sex a few times and it's been nothing to worry about. My periods are messed up and if It's the same time as last month then I'm late and I get stomach cramps and I'm feeling tired. I've looked it up and I know these are signs of pregnancy. He says that he didn't ejaculate at all but this doesn't really comfort me because we've learnt all about sex and stuff at school. I'm really scared that I'm pregnant and I know my Mum and Dad will kill me if I am.

Am I just being silly or is there a real chance that I'm pregnant?

Please help me, I'm so scared.