着てた

was wearing, wore

→ 着る
着 wear, put on + て Te-form (conjunctive form) + た Past tense
verb · informal, past tense Rare #42,138
was wearing, wore Colloquial contraction of 着ていた.
JA: 昨日は青いコートを着てた。
EN: I was wearing a blue coat yesterday.
Conjugation of 着る
Indicative past
着ました着てた

トムが着てたのは青いセーターじゃなかったよ。

What Tom was wearing wasn’t a blue sweater.

普段は修道院で着てた服よ

It’s what I usually wore at the convent.

— 燃ゆる女の肖像 (2019)

トム、みすぼらしい服を着てたわ。

Tom was wearing shabby clothes.

この鎧を着てた奴は運がなかったな

The guy wearing this armor was out of luck.

— 荒野の用心棒 (1964)