When I told my parents it wasn't the ideal time, I wanted to tell them one night with the OH, but my sister had friends round so it obvs wasn't the best time. On my way out I said to them were they gona be in the next day so I could have a chat. Not the best thing to say as I then had to tell them on my own. Mum said she wouldnt sleep if she didnt know. Just sat down and came out with it. We'd been trying for ages, but had been through a bit of a rough patch with me moving back in with my parents etc. They kinda knew anyway, so they weren't that suprised, more worried about me and how i was gona bring up a baby. They wouldnt speak to my OH and he had the front door slammed in his face a few times, basically they couldnt handle their little girl growing up (I'm 20 in july).
They've come round to it now and they're still worried, you're parents will worry about you for the whole of your life!!
Good luck with it all and with telling them, it wont be as bad as you think!