20 week scan approaching

I have my 20 week scan on Tuesday, I've gone from being extremely excited to find out what we are having to extremely terrified in case there's something wrong, this is my third pregnancy and the furthest I've ever got, it still doesn't feel real, and feels like I'm in some sort of dream. I've not really felt any massive movements just the odd poke or prod and of course stretching pains, just wish I could stop worrying and start enjoying being pregnant!