Second Pregnancy

So I'm a single mum to a little girl (20mo). I separated from her father and everything's been fine so far. We have 50/50, and coparent as best we can. Shortly after we split, I found out I was pregnant again. My ex is the father as I haven't been with anyone else. I've told him and he's happy and supportive which is great.
But this is all so new to me (the whole single mum gig that is). My first will have just turned 2yo before bubs is due. How do I go about the transition from 1 child to 2? And what about custody as the father obviously wants in on baby's life and I'm more than happy for that as he's already a great dad. Anyone been in a similar situation and can share their advice and experience?
This pregnancy has been so different to my first as well. This time round I'm being hit by morning sickness and cramps. My first was pretty easy going and she slept through the night from day one. Is it true the next one is polar opposite? And is it true the labour times get shorter? Again first was easy, 2 hour labour from when waters broke to her being born.
Any words of wisdom or anyone care to share their experiences with second pregnancies and labour?
Sorry I know I'm asking a lot but I'm feeling so very overwhelmed by it all