hi sonu, you and your husband definately have the deciding vote on this - it will be your blood sweat and tears, your hard work, and your lives that will change. Every baby is extremely hard work - and is a wonderful, life enhancing miracle too - but its your choice whether to embark on all that again or not.
I see that its nice for a child to have a sibling but this isnt more important than anything else. and there is also the argument at this point that with at least 5 years between your child and any other possible baby they wont really be playmates in the sense that your friends probably anticipate.
I think if you've made that decision though it might be an idea to use contraception - as probably, sooner or later it will happen to you. Maybe leaving it to fate is a gamble that might take the decision from you but really having a child is the most massive thing there is, better to have fully made that decision together.
There are positives with having one child - like you said she will be your focus and you will give her everything you have. You dont have to apologise for that.x