Demi Lovato's Ex Max Ehrich Going to Rehab After Domestic Violence Arrest

Demi Lovato's ex-fiancé Max Ehrich says he's going to rehab after his domestic violence arrest ... and it sounds like he needs help, based on what he's telling us about the leadup to his arrest.

Max tells TMZ ... he was high and in psychosis when he had an altercation with his mom that resulted in him being hauled off to a Florida jail on a battery charge. He says his mom was trying to get him to stop huffing nitrous oxide.

The "Young and the Restless" actor says he went to Florida to stay with his parents ... after allegedly being kidnapped in Los Angeles last week by 3 gang members. He says his alleged kidnappers introduced him to nitrous, and he was high on nitrous for a week leading up to his arrest.

Max says he is under a 72-hour psychiatric hold in Florida under the Baker Act ... and when that's done, he says he plans to spend at least 30 days in a rehab program.

We broke the story ... Max was arrested Tuesday night and booked into jail early Wednesday morning in Port St. Lucie after he was accused of domestic violence.

The police report said Max got physical with his mother while abusing nitrous oxide. Max was streaming live that night ... and the video appears to show him huffing nitrous while his mom breaks down in tears. He also appeared to be inhaling nitrous when talking to cops.

Police say Max's mom told them her son "heavily abuses inhalants" and had consumed nitrous oxide before turning violent during an argument over her phone in their house. Cops said she told them Max chased her outside into her neighbor's backyard, pushed her to the ground and kicked her in the thigh. His mom did not suffer serious injuries.