You’re only 23 🙂 Don’t try looking too far ahead into the future at this moment, but take it one step at a time. You may feel financially insecure right now, but you never know what might arise 5 years along the road.
You indeed do not need to have 10 kids one following the other, but if you are blessed with a 3rd one, be thankful and God will provide the rest.
p.s. I am almost 23 y/o and have a 3-months old daughter with identical fears to yours. It is ultimately scary and sometimes stresses me out to the most extremes – not only the financial aspect of it, but the whole idea of having more than 2 kids in a world where 2 is to many. I would like at least 3 kids and know 100% my family will freak out and consider me a mental case. It’s tough hehe