Flyysoulja is getting help -- checking into rehab months after suffering a drug-induced psychotic episode ... TMZ has learned.

The Island Boys rapper tells us he's heading into detox to address his substance issues and focus on becoming "a better version" of himself and a better dad.

Flyysoulja tells us ... "I'm going to detox right now to get the help I need. I can't wait. I've been here before, but this time I’m going to take it a lot more serious."

He calls the decision "good news" and a "very powerful moment."

As we reported ... Flyysoulja was detained in Florida last year under the Baker Act after police say he took multiple substances and suffered a psychotic episode. Officers at the time reportedly mistook nail polish for blood and feared he might try to harm himself.

Afterward, Flyysoulja said he was grateful to be evaluated but clarified, "I have a substance issue -- not a mental problem."

Now, he tells us he’s determined to come out stronger.

Good for you, Soulja! We're rooting for you!