Fake people are not liked by many, or atleast not liked by genuine people. Wouldn't a child who grows up, rather know his mom was unhappy about her decision and admire her honesty, rather than know she faked it and had no respect to tell him the truth? Plus the mom is perpetuating the happiness mtyh if she lies. Maybe these women are in their situations because their mom's lied to them about parenthood and happiness. Why wish the same existance upon your own child? Why not do your best, and when the child is old enough explain how hard and lonely parenthood is? My suggestion is to not have anymore kids, you are unhappy, not to lie the child you have, and to do the best you can. If you can't do it, adoption is an option and I amdire any woman strong enough to admit she needs to give the child up for adoption.
The myth of how great motherhood is, is perpetuated by people who lie about it, why continue with this downward spiral of unhappiness? Be honest about it.