I'm going to be 17 soon. I am shortsighted. My left eye power has been -2.75 and my right is -3.25 since I was about 10 years old.
I go for eye tests almost every year and my eye power has still been about the same. Serious.

Since I was 10, I did not like to wear my glasses because I find it quite irritating when it slips off. Also, I thought I did not look good in it. So I only use my glasses when I need to read the blackboard or when I use the computer or watch television or sometimes when I study. On normal occasions, I don't wear them.

The issue now is yesterday, I broke my glasses. I've been thinking about getting contacts. But I'm very lost about whether contacts is better or glasses is better. Or none. Because since I'm having an upcoming major exam, I won't have time to use the computer or watch television.

The only thing right now is just this year I have been getting headaches(previously I don't) and I wonder whether my eyes have been strained because of my on and off usage of glasses. And my frequent use on computer. Also, I've read that if you don't depend on glasses on contacts, it will help improve your eyesight. Yet I've read also about if you don't wear glasses or contacts, your eyes will be strained and you'll get headaches.

So my question is, what should I do?

No, not using needed glasses will not "improve" your eye sight,

The need for glasses are also from different and various reasons. Most people, who need or use glasses, will slowly need to change their prescription.

Being vain about looks, merely hurts your eyes if you are not using them on a regular basis.

Contacts or glasses is merely a preference, assuming you can wear and use contacts.

Your eye strain can be from on-off usage, not updating regularly, computer use without breaks, over use of computer. There are a number of reasons. With this eyesight that you listed you can be fined for driving without correction. If you are prescribed lenses, wear them.

Not wearing correction will not make the eyes work harder and then heal themselves as some people believe... This will get you hurt, into trouble or many other things can occur from one not being able to see properly while performing everyday activities.

Thank you so much :) I understand now.

Thank you so much :) I'm not driving yet, in my country I can only drive after my 17th birthday.
I just got my contacts today, and I'll be getting a pair of glasses too.

Good to hear.