Amanda Bynes is definitely an overthinker... at least that's the statement she's making with her latest fashion choice.

The former Nickelodeon store was spotted Monday in Los Angeles ... running errands with a friend.

Amanda's wearing an "Over Thinking" shirt ... matching her black boots and black leggings with the brown, long sleeve top.

She's carrying a small, white purse ... but the stylish accessory doesn't seem to fit all her things, because she's got a couple items in her hands.

Amanda's occasionally spotted around L.A. these days, and she's not exactly shying away here ... keeping her sunglasses hanging from her shirt instead of covering up her eyes.

She's also got her trademark bleach blonde hair and septum ring ... and her face tattoo is clearly visible here.

Amanda looks like she's deep in thought ... like we said, she's an overthinker!!!