Guy's Behavior

Why did my guy friend ask me my bra size then say he was just "Kidding" everytime I got offended?

Okay so me and my guy friend were talking, and I was basically telling him my story of my vacation to a hot tropical kind of country 5 years ago. I basically told him that it was too warm to even wear clothes to sleep at night so I Just wore a vest. Then he was like "Well how was your breasts?". "Did you wear a bra?". "How about your mum?". Then I was like "I didn't wear a bra that time". Then he was like "Hahaha yeah you were 11... isn't it budding that time?". "Hahah how about now?". Then I was like "Oh please move on". Then he was like "Kidding hahaha". I was like "Of course I have boobs now lol". He was like "Haha what size?". "Lol just wondering". "36b?". Then I when I took long to respond he was like "Haha forget it". I noticed one thing though... He kept saying he was Just kidding whenever he sensed I was offended. But however kept it going when I answered all his questions.
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He's 25 by the way
Why did my guy friend ask me my bra size then say he was just "Kidding" everytime I got offended?
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