Inflammation or weight gain?

I haven’t taken my shot in 2 weeks because I had to have surgery. I’m due to start again tomorrow. I’ve been maintaining my weight this whole time and didn’t gain anything. But I woke up this morning and I’ve somehow gained 7lbs. Is that even possible? How can I be up 7lbs that fast when I’ve been maintaining the last 2 weeks? I’m so confused and frustrated right now.🥲