Pre-natal depression

I'm almost 34 weeks pregnant and it started at the beginning of September when my 3 year old daughter started pre-school 3 times a week instead of just 1, I just cry all the time, I can't even explain why I'm crying, I feel like there's no real reason just my head tells me I need to cry. I look forward to weekends when my fiancé is home, but then I dread them being over because I know it's Monday and my daughter doesn't go to school then so I can just stay at home and cry (I try to visit my sister every Monday so we're not stuck at home). I'm so scared about having this baby because I don't know how I'll cope with 2 when I just want to cry all the time. I need advice, I don't want tablets I just need some reassurance and help with how to feel normal. Please anyone? :(