Feeling down!

18 weeks and last few days been feeling so lost and depressed... I'm worrying about whether I'll be a good mum and being 24 I feel like people will just assume I'm inexperienced and hopeless. Can't stop crying, I was so happy before that we planned our baby but now I'm worried that everything will go down hill after bubs is born... Doesn't help that my husband is constantly on his computer and I feel really lonely at home.. What is wrong with me?