Weight gain post loss?

Anyone else experienced unexpected weight gain after your loss? I was thrilled that I hadn’t gained a single pound in 12 weeks of pregnancy (my BMI is in the obese category and my personal pregnancy weight gain recommendation is only 4-8 lbs the whole time - meaning I’m supposed to LOSE weight actually while pregnant) and I saw that as a sort of silver lining around my loss, since my first loss I’d gained ten pounds while pregnant (I let myself eat whatever - zero self-control). I thought, well at least I didn’t gain any weight from being pregnant this time. Then in the seven weeks since I’ve gained TEN POUNDS. Like, I didn’t eat a crapload over the holidays or anything, and I’ve actually been exercising a ton and drinking lots of water and I have no clue how I could have gained so much so fast. I had postpartum hypothyroidism with my daughter so I’m hoping that isn’t back but idk. Anyone else have a similar experience?