My face skin became saggier than weeks ago. i wasn't drinking enough water and eating well, had insomnia, lost weight. will my skin go back to normal if i sleep well and drink water? i'mm 22?

Yes it will.

Being better hydrated will restore the turgor of your skin. For healthy diet: http://www.choosemyplate.gov/., exercise 30 minutes/day, drink enough water daily so your urine is mostly colorless, have safe sex, no tobacco alcohol weed or street drugs. Get HPV vaccine. Wish you good health! Safe sex: https://www.hopkinsmedicine.org/health/wellness-and-prevention/safer-sex-guidelines