Can I retract a settlement agreement that I signed under duress?

Question Details:

I signed a separation agreement. I gave in to all my ex-wife's demands because I'm afraid she will take away the kids from me completely. She did it once so she has the control in doing it again to hurt me. One of my worries is the house property that I quit claim. We discussed and agreed that I quit claim because i want to give half of it as my investment for the kid's college fund but it is not written in our agreement. Can I still get the half value of the property even if I quit claim in the contract? Important Notice