To 'cure' gingivitis, first step is to go for scaling. This is to get rid of calculus around the neck of your tooth. Do this at least once a year.

Secondly, you must maintain good and consistent oral hygiene. Brushing twice daily is sufficient. More importantly, effective brushing. Look up youtube to learn how.

I would suggest using soft toothbrush. If you use too much force when brushing, it may lead to abrasion of the neck of the tooth, causing even more problems in future.

Floss after meals.

Do you smoke?

Gingivitis will eventually develop into periodontitis. This is when your gums start to recede and tooth becomes loose!

If I remember correctly, it is due to your age (adolescence) causing hormonal imbalance, resulting in increased blood flow to your gums. And because of this, your gums may be more sensitive to irritation. Also maybe your body immune response is slightly altered. As you age, those swellings will be less frequent provided you maintain that consistent oral hygiene. Don't worry too much ok?

Pretty much the same reason why pregnant women have very high incidence of periodontal disease.

Remember, over zealous brushing will cause more harm than good. =)

on the other hand, i would highly recommend that you stop using that toothpaste as it does not contain any fluoride.

improving gum health, at the expense of tooth decay? would you gamble that?

just mild inflammation of the gums, surely no pain.