Hi there
I don't have very much advice but thought I could at least offer some solidarity.
We are in exactly the same position. We were discussing no 3 and I had just started to think "maybe not" when I found out I was pregnant.
I have been up, down and all over the place since finding out. Its confusing because I have been soooo broody for the past couple of years and was only thinking we shouldn't go ahead for practical and financial reasons.
If I'm honest, I know that adore my kids and love the fact that I have the chance to do it all again, but am worried about the effect it will have of the rest of the family.
However, I was one of 3 and so was DH. Neither set of parents had much money and we came through it ok, in fact we both have lots of happy memories that have nothing at all to do with whether our families were rich or poor, but more to do with the fun we had together.
My DH has been going through all the same thoughts and worries as me but the most important thing is that we have kept talking about it. He too wasn't that keen on having another but I had just managed to talk him round and then got cold feet myself! Didn't change his reaction when he found out it had happened though!
At least we have a good few months to keep up the dialogue, make plans and get organised and I am trying to remain optimistic that we will get it all sorted out - emotionally, financially etc etc before the due date!
I always think things are easier to face when you are as in control as possible and so I've already started costing things out (we have got rid of all our baby equipment!). I found that most things can be bought fairly cheaply - there is even a cot in IKEA for £29.00! I am buying maternity clothes off ebay and will research any/all major buys and get the best deal as we go along. I'm planning to save money by buying plently of white sleepsuits that come in multi-packs and a couple of nice jackets/cardigans to go over the top. Oh - and of course breastfeeding is free .
I suppose the first few months will be hard, but that's such a small part of a childs life it will probably be tough at the time yet gone in a flash.
I really think communication is the key with DH, it is important he understands your worries and how you feel so that he can support you and so that neither of you feel alone with your worries. As I said to my DH the other day "I might be pregnant but we are BOTH expecting a baby!"
Sorry, I haven't been able to help much - just wanted you to know that you are not alone in feeling like this.
Hope you are able to reach a point where you can be a bit more optimistic and start to enjoy your pregnancy soon.