Please how did u get skinny?

I am 23 5'1 146 -142 lbs

i need to get rid of this crap FAT. second baby I just got fat and not good
I been exercising about 3 week eplitcal, treadmill 15 15 total of 35 I don't want to over due it cause I'm exausted
i need and want to go for 120 again help

i very little eat fast food and breadth
Please how did u get skinny?
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