What is going on with my body! :(?

It's pretty tough to gain 2.6 lbs of muscle in a week even if you are eating right and training hard. Everyones weight fluctuates, doesn't mean you've gained fat or muscle. I wouldn't worry about it at all. I know I will weigh myself and I will be 4 lbs heavier than i did 2 days earlier but I will still look the same. Keep up the good work because losing 8 lbs is hard for anyone.