Brian Austin Green's getting real about a blast from his dating past ... opening up about his time seeing Tichina Arnold and revealing she was adamant their hookups stay strictly under wraps!

Speaking on Deon Cole's "Funny Knowing You" podcast, Brian said keeping the romance a secret triggered deep insecurities, especially since he already felt like he didn’t fully fit into or feel accepted by the culture around him at the time.

Brian said it really sucked feeling like the person he was into didn’t even want her pals knowing they were together ... and, while she eventually became more open about it, he realized the relationship wasn’t healthy, especially since it didn’t even start from an honest place to begin with.

The trip down memory lane came after Tichina shared her side of the story ... explaining on Deon’s podcast a few weeks back that she ended things because she noticed Brian had a pattern of dating Black women and felt he’d ultimately end up with a white woman anyway.

Because of that, Tichina said she took herself out of the equation and realized she wanted to be with Black men -- but she made it clear it didn’t change her opinion of Brian, saying he's a great human being.