star Seth Peterson’s a reckless druggie who abandoned his pregnant wife for a 22-year-old woman … so claims his pregnant wife … and now, shocker, she’s filing for divorce.

Kylee Cochran filed the docs in L.A. citing irreconcilable differences. Kylee is now 7 months pregnant and wants a judge to give her full physical and legal custody of their kids, including their 5-year-old son and 8-year-old daughter. She claims Seth is already okay with this, and agreed to give up all custodial rights.