Barbie - I have been where you are now. My dh had the snip when dd3 was less than two weeks old. He was absolutely devastated when 18 months later I was pregnant with dc4.
I know I don't have the close age gaps you have and will have, but the pregnancy/baby was not planned.
He is here now and as someone else said, we would not be without him. My whole life had to change in order to have him, but I could not consider abortion. This was made worse by my dh who wanted me to have one.
You will manange. We have survived. Our son is now 19 months and we are all still here and just about scraping by financially.
Like you I worried about the kids and the lack of time I would now have with each one. The girls love him, there is 25 months between dc2 and dc3 and they are as thick as thieves. They sometimes have their disagreements but on the whole play together and I don't need to entertain them at all.
There are no arguments about what channels to watch, what to do for a day out, where they want to go. They both always want to do the same. Also, miraculously enough, when they have friends over they all seem to play so well together.
Whereas, there is 3 years between dc1 and dc2 and they are clearly at different stages. Dc1 never wants to do the same thing as dc2. When dc1 friends are over she doesn't allow dc2 or dc3 to play. It is all so awkward.
I am not advocating close age gaps just because the logistics of it all are so much easier once the kids are past the baby/toddler stage. But now, that mine are past baby stage, I can see the benefits of the closer age gap.
Family and friends may surprise you and really help you out.
Also I have been pushing a pram/buggy now for over 9 years, with at least still another 18 months to go. I will be pushing prams/buggies constantly for nearly 11 years of my life. You only have to do half of that!!
You will be fine, stop worrying about others. It is your family and life. You are not the only person to have four children and you won't be the last. You have managed and coped with three, you will do the same with four.
I am sorry I don't mean to sound hard. We didn't tell anyone until well after I was clearly showing, I was about 22 weeks. Obviously I was embarrassed that people would think the father was someone else, and dh had told the whole world that he had the snip. Prior to this, every male he knew, he advised them to get the snip, whether they wanted his advice or not.
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Deep breaths, and it will be fine.Oh and we only have a tiny house, 3 beds and I drove a corsa and changed it to a Zafira on dc4 arrival. Obviously, a second hand one.