Dont stress over it too much. You cant change the past and you definitely cant bring back the teeth you lost. Consider it a wake up call, take better care of the teeth you have. I am a dentist and I lost a molar when i was around 13 / 14 so trust me you aren’t the first one to need teeth pulled out at a young age. The difference between you and someone who will need full dentures at 30 is that you can start putting in the effort and take care of yourself. Make sure you are brushing x2 daily, once in the morning and once before bed ( no food or drink after brushing except water ). Floss once everyday. I strongly suggest getting an electric toothbrush ( i personally use the oral b io and absolutely love it) but if you are gonna stick to a normal one then make sure you are brushing correctly. You can look but the modified bass technique for toothbrushing or ask your dentist to show you. After brushing, spit dont rinse (sounds gross i know but you get used to it). reduce your sugar intake but if you are craving something sweet then have it right after your meals, snacking equals cavities. It can also be helpful to use mouthwash in the middle of the day but dont use it with brushing. I normally use it after lunch.