You became a mom when still just a child yourself. As you suspect, the age at which you have your three precious daughters (yep, that babe in your belly right now is a girl, too) will affect everything you do and are throughout your life.
That can be a good thing, though—if you allow it.
In hopes you will indeed allow it, I have some advice for you. Despite you being stubborn in ways many have yet to realize, I do hope you'll take my advice to heart, act on it.
My advice is this:
Stop being so scared. You're scared about what's to come, what people think of you, what your girls—hell, what you—will grow up to do and be. You're scared of the other, older moms who seem to know and have and be so much more than you. You're scared of not knowing enough, not having enough, not being enough.
Well knock it off! There's no reason to be scared. Well, there is reason sometimes. But there will soon be an advertising tagline that says, Feel the fear and do it anyway. Do exactly that—always, in all ways.
Question authority. That principal who tells you it's okay to send your barely five-year-old daughter to kindergarten? Question that. That doctor who tells you tubes in a child's ears are a thing of the past? Question that. That same doctor, who tells you your daughter has an infection when it turns out to be a <cuss> hernia? Question that. When you're assured a negative amortization loan is okay, question it. And when an editor rejects your work, question that—then send it to other editors and never. ever. give. up.
Don't take the job. A few years from now, you'll be offered a job by someone you consider worldly and wise. Don't take it. The damage to your self-esteem, marriage and more because of "friends" you make there is so not worth it. Trust me. Yes, your household desperately needs the money, but Just say NO! (another slogan that will soon be a pop culture hit).
Brace yourself. I know you, I know you'll ignore the advice above. So brace yourself. The stress caused by the consequences of that bad choice will wreak havoc on your health in ways that will affect you each and every day for the rest of your life. Seriously. But know this: It's not as bad as doctors first tell you. You will walk again. You will see again. In fact, your neurologist will one day tell you you're a miracle. Trust that doctor. And trust that you will be okay.