Congratulations!
It'll be fine.
When I was having my first, I joined a parentcraft class and after we'd all had our babies, we'd meet up from time to time. Anyway, 7 or 8 months after we'd had the babies, we met up in the pub and one of the others announced she was expecting.
We all said she must be off her rocker 
Well. I got mine because although I didn't know it, I was also pregnant and we were back in the hospital giving birth again at the same time. We both had become pregnant 6 months after our firsts were born.
So there's 15 months between my two. They are now 14 and 15 years old.
It's been fine. Honestly, just - fine. Tiring, but that's being a parent.
Everyone is different but I really liked getting the baby stuff done in one long stretch, instead of having to go back to it years later.
Accept and ask for the help you want and need. That would be my advice.