Suggestions and advice for eye care?

Hi guys. Here's the case. I read a lot. Too much, I'm beginning to think. When I overflowed my bookshelf, I turned to ebooks. I transfer them to my mobile( Lumia 820) and read late into night. I've been doing that from the past one year, and now I think it's taking a toll on me. My eyes start hurting after a while. Along with that, I'm also active on FB, instagram, whatsapp and wattpad(and YA too, sometimes). And my school is considering switching to ebooks from this year.
I don't want to visit any optician, nor do I want to wear specs or lens. I'm sure I'm not that damaged. Please give me tips and suggestions to undo what damage I've done.
PS, I'm no 'studious geek', who is cooped up indoors all the time. I do step outdoors.I'm out half the day, so I get exercise and all that.

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