19 and unsure of what signs are.

I am 19 and this is my first pregnancy. I'm 39 weeks pregnant and I have a jelly like substance that keeps appearing when I wipe, I have terrible cramping in my back and also, my baby is moving a lot and there is a lot of pressure in my vagina.. I occasionally get a period like pain in my abdomen, I was just wondering whether this is all part of my body getting ready?

sounds like your losing your mucus plug and your body is getting for labor

Mucous plug! Get ready! Congrats!

Your age isn't really relevant hon, I'm 23 and I haven't a clue what any of this is supposed to feel like, pretty much like every FTM!

It could be your mucous plug, but that in itself isn't a sign of labour. If you can time your pains and they are consistent, then you may well be in labour!
If not, you're probably right that it's just 'getting ready' pains.

Yeah the pains are now getting more intense and I keep being sick... Fingers crossed!  

Congrats! Let us know what happens!