Am I Losing Weight Healthy Or Unhealthy?! Read Inside?

for the past month or so, i’ve changed my eating habits. i won’t say i dramatically change them, but i cut out all soda and sugary drinks, i mostly drink water and milk. i cut out a lot of junk food, i used to eat chinese food twice a week pizza twice a week and i would get like two chocolate bars and three bags of chips every night. i don’t do that anymore. i only had fast food about two times this month and it wasn’t a lot, i definately don’t miss it, i felt sick after eating it. i only get junk food once a week now, to stop my cravings, and it’s only like a crossaint or a bacon egg and cheese, or one bag of chips. something yummy to satisfy my stomach, just once. and i started eating fish, and a lot of fruits and vegetables, and cut out the french fries.
i wouldn’t say i’m dieting, i really just think i switched to a healthier diet. i don’t even excercise or get out much.
i was 120 pounds a month ago, now i’m 112 pounds.
i was thinking wow, losing weight is so easy.
but than i got a blood test and i’m extremely vitamin D deficient. i looked up the symptoms and it says weight loss is one of them. losing weight because of health problems does NOT sound like a good thing. do you think this is why i’m losing weight?! or is it because of my new diet?
i’m so confused, i wanna be losing weight HEALTHY. i’m 5 foot 1, 112 pounds, and 17 years old. my goal is 105 pounds.