No great words of wisdom but didn't want to leave your post unanswered. My only experience is that with my ds2 I never got the rush of love that I felt with my first, it just sort of crept up on me. I don't think I really felt that I loved him, until the first shock, when he was ill, and vulnerable, and then I realised that I had been loving him for a while, after all.
I'm not surprised that with three older children to look after you may not have time to feel the same as you did before. I take my hat off to anyone who can cope with such a houseful!
I wonder if there are any undealt with issues affecting you too: are there financial concerns now that you have another little one? Was the birth particularly difficult? Was this baby planned or a surprise?
You are clearly worried about how you are feeling and your hv's advice doesn't seem particularly helpful. More sleep is a good solution to most things, but if you are still worried, then don't let her fob you off. This can be a symptom of PND, for which you will be able to get help and support if you still feel unhappy. And, of course, there will be other posters along with more valuable advice soon too.
HTH - off to Sainsbury's now, but will try to check in later.