Demi Lovato‘s ex-fiancé Max Ehrich was put under another psychiatric hold after fans grew concerned, again, about his alarming behavior online over the weekend … TMZ has learned.

Max tells TMZ … he was taken by ambulance to a mental health facility in southeast Florida on Saturday after his Instagram followers raised red flags to police over a string of provocative photos and erratic posts on his social media. He says some of his fans feared he was suffering a nervous breakdown, and they alerted authorities.

We’re told cops responded to his parents’ home, met with Max, and determined he needed further evaluation … so he was transported by ambulance for psychiatric assessment under Florida’s Baker Act. He remained at the facility for 72 hours.

We broke the story … Max checked into rehab last month following a domestic violence arrest. As we reported, the police report stated he got physical with his mother while allegedly abusing nitrous oxide.

Max was streaming live and the disturbing video appeared to show him huffing nitrous while his mother broke down in tears. 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.

Max and Demi were engaged briefly back in 2020 … after just 4 months of dating, he popped the question … but two months later they separated for good.