Matthew Mindler's mom says he struggled with severe anxiety issues for years, and yet ... prior to his suicide, she says he seemed to be enjoying his 1st week of college.
The late child actor's mother, Monica Mindler, tells TMZ ... Matthew moved into Millersville University on Aug. 19, and things seemed to be going very well, until he disappeared.
Matthew's mom says he kept in constant contact with her during his first few days on the Pennsylvania campus, and he was busy. Monica says her son told her he met with an advisor about starting a campus computer/programming club, had an upcoming job interview with the IT department and was making friends.
As we reported ... Matthew, who starred in "Our Idiot Brother," never returned to his dorm room Tuesday night, was reported missing Wednesday, and found dead Saturday near campus. The coroner says he died by suicide.
Matthew's mom says their last text message exchange was Tuesday night, when she told him she was planning to pick him up Friday to spend the weekend at home. She wanted him to come home and relax for a few days, knowing he struggles with "crippling anxiety."
Monica tells us she texted him Wednesday morning, but didn't get a response -- her messages went through as texts instead of iMessages, suggesting his phone was off or in a bad service area.
Monica says she later contacted Matthew's dorm at MU for a wellness check, and got in touch with his roommate Wednesday evening, but she was told no one had seen her son and people at school were concerned.
By Thursday, Matthew's mom still hadn't heard from him and she drove to campus and got the police involved.
She adds ... "We appreciate the support, concern and outpouring of prayers from Millersville University, the students and the community. My heart is crushed and my mind cannot yet fathom this reality."