I felt the same way after level2... I figured out I was doing a lot of the stuff wrong kinda... The planks are easy to do wrong, if your hands are not directly below your shoulders on the ground you arent in the correct position and you aren't working the muscles you are supposed to.
also in the part where you do squats front then back, you have to make sure your knees don't go past your toes or you won't be working the muscles in your legs just injuring your knees.
Level 1 kicked my butt everyday I was almost scared to go to level 2, then i felt the same way about going up to level 3... I'm doing level 3 now, but most of the modified stuff, it's kinda like level 2.5 i guess
SO just make sure you concentrate on your form and level 2 will surely start to hurt as much as level 1