Hi Blonde Assassin,
I just wanted to add my story to this because i was in a similar situation to you.
We had a beautiful 3.5 year old daughter who was always a really good sleeper (well like you put her to bed and she didnt wake till morning) and i had always wanted another child but i had a feeling the next would be a whole different story to this child.
I can remember being on holidays in Thailand and I said to my partner how abouot we only have her and no more.

anyway long story short we decided to have another and its a little boy who we both completely adore! he is now 20 months old. but....as i was dreading he wakes ALL the time at night, he runs away from us, he is as cheeky as can be! but i tell you what how could i possibly regret him???? he is my son, my blood. You know those things are going to fade and he will eventually sleep and stop running away.

and the age gap is 4.5 years and my daughter adores him, helps me out with him. its been so wonderful for us all as a family to watch him grow up. My daughter shares in all the firsts with us. Its just really special. You will never regret a child you have....why? because they are yours....plain and simple.

this is completely your decision just dont make your decision based on the baby stage because that is not forever....Good luck with your decision. xx