Your own body

Sammie • 22; married👰🏻🤵🏻; TTC 2 years 🍼👶🏻
With my own body I tend to look at it  and think how have I got this unfit, I've always been a size 8 but within the past two months I've gone to a 12 I'm not angry about it cause I'm quite confident but I don't understand how I've gained that much that quick, I eat the same and excersise the same so can't be that .. Can it?