Jax Tayloris firing back at his exBrittany Cartwright‘s plea for a restraining order … and asking for his own protection from her … TMZ has learned.

TMZ obtained a petition for a restraining order filed by Jax, where he asks a judge to order her to stay 100 yards away from him and not contact him. He also asked that she stop interfering with business deals he has in place.

He claims she spread malicious lies about him on the internet and social media … and even started to contact potential employers and partners to threaten them with public admonishment or “worse if they hire me or associate with me in any way.”

Jax claimed Brittany’s actions cost him a role in a Fox television series “Special Forces” that would have paid him $175K and would have been his “comeback” role. He said she has targeted six of his employers or partners this month alone, which he says has forced the companies “to distance themselves from me out of fear that she will create a public backlash against them.”

In addition, he claims Brittany has been “grossly negligent” with their 5-year-old autistic son and has been refusing to work with him on his medical needs.

Jax said he’s been sober for nearly 2 years and continues with weekly therapy, claiming he’s done his best to step up as a father. He said he has been voluntarily submitting to random drug testing at her discretion.

He claims after starting his relationship with Brittany he learned she is “massively unstable and an alcoholic.”

He said she often called him a “asshole,” “loser,” and “dirty dick.” He said Brittany launched a “full-on attack” against him after learning he was in a relationship with his publicist, Lori Krebs.

He said she has gone scorched earth on him due to his romance.