Why Am I So Paranoid?

Why am I so paranoid?  I feel like my ex-husband is out to take custody of our son from me.  He and his mother has been accusing me of turning our son against him and his family ever since our son was born.  I feel like I can't do anything right when it comes to making decisions regarding our son.  Whatever I decide, it's always wrong where my ex-husband and his family is concerned.  I feel like I just want to drop our son off at his home and let him deal with all this.  I feel like, "why should I even bother when whatever decision I make will always be wrong?"  Sometimes I just don't know what to do anymore?