You know how when you raise skills and it says you have to rest to level up? What if you keep raising skill soo then can you level up the first time and then sleep again and level up again? Or it doesn't happen like that.

The skills will count towards your next level-up... but they won't count towards any bonus multipliers at the time of that next level-up.
So it is always best to rest and level-up as soon as you need to.

But, yes. You can level-up twice in a row if you let the experience add up over 20.