Hi! I am pregnant for the 4th time and this pregnancy has been hard so far too. I know about the fear and worry that you described. I may have a different background though. My 1st daughter was born 2/2001 the second 7/2006 and I miscarried in 7/2007. I also have a thyroid problem (treated NOW and under control) and am 35yo. I was told from the beginning why I was high risk not that this can work. I am due July, 25th.
Let me get back to you. If you are 10 weeks your miscarriage "chances" are going down.
The family dynamic will change but you will set the tone. If when you bring baby home and you won't let the 4yo help, touch or do anything with baby or you while you are caring for baby then things can go bad. BUT If you encourage the 4yo to hold (supervised), love, help, care for baby then she will be better off. Some children go through the jealous thing but lots of love and attention from you and Dad will get her through. You encourage love and the children will still fight but love each other at the end of the fight.
Finances: I worry too! We are a 1 income family soon to have 3 children! OUCH to the family budget! We make do! You will too! We have had to not do some things we wanted such as kitchen remodel, multiple vacations and eating out often but it's fine. Our kitchen is UGLY! but works, we go on 1 nice vacation every year and eat out once in a while. we have found ways to "eat out in" too. For instance: Walmart sells great premade (fresh made too) pizza. At $7 we buy that, a bottle of soda and have fresh hot pizza at home! We are in a finacial crisis in America but that baby will be loved and cared for anyway! He/she will add so much to the family and you will find a way finacially to give your family what they need. I have found what I thought I need is not what I really need.
Finally the exhaustion. It is pregnancy! Talk to your doctor and get checked for anemia and take your prenatal and if all is fine then you will learn how to deal with it. I can't give you hope that it will go away. For me it hasn't but for some it has. Each body is different but think of the beautiful baby you will hold and it makes it easier to handle!
Adding another baby to your family is a blessing sent from God! That baby will bring sleepless night and worry but will also bring joy, love, happyness, and laughter. seeing your 2 children interact will annoy (when they fight) you and thrill you when you find them curled together playing nicely. Love is multiplied when someone new comes into a family. IT never divides. Your time will divide, your budget for kids stuff will divide, a room may divide but LOVE MULTIPLIES!!!!
I don't know if this will help at all. If you still feel super stressed maybe a counselor would be helpful but take it from someone who knows! YOU CAN DO THIS!!! A.