As if I don't have enough to worry about without my youngest making up such things.
I understand this meaning:
without my children making problems, I have nothing to worry about.
am I right?
No. As if I didn't have enough to worry about means that the mother in question is despairing at the fact that in addition to all her other worries, her child is now making up things (i.e. telling lies). It is a colloquialism that couches itself in terms of an appeal (to a non-specific higher power) to take some of her worries away.