Is it too early for me to know that I don't want more children?

I was absolutely desperate for a child for years before I had my little girl who is now 4m old, but I think people thought I was desperate for childREN and now keep asking my husband if and when we're having more!

My husband really wants another but I'm pretty sure that I don't, but could I change my mind in a couple of years?

I've adored every minute with my girl and I love her like I've never loved anyone or anything before, I feel like I couldn't love another child like I love her and it wouldn't be fair.

Is the newborn stage any easier the second time around? We had such a difficult time with LO because she had such severe reflux, we had to stay up with her doing shifts 24hrs a day for almost 6 weeks. Is this normal?