Early weight gain...

Anyone else already gaining weight? It's only halfway through week 6 and I've already gained 4 lbs! I seriously don't get it, I'm not eating more in fact I'm eating less. I hardly ate at all last week because of the nauseous but my scale just keeps going up! I know it's way too early to be putting on the lbs, and I'm already very overweight to start with. Anyone else going through this?