Is there any way to increase your reading stamina?

Yes, by reading.
Reading tires and reading for a long time needs practice. Start small, reading for about 15 minutes. When you get used to it and see you’re not tired any more, prolong the next reading session to half an hour. When you get used to that, prolong it to 45 min. And so on.
It’s like exercising your body. Start small, and then gradually make the training harder.
If it helps, read about subjects that interest you. That will keep you motivated and prevent you from falling asleep.
Just gon’t go too hard imiediately. It doesn’t have to be 15 min like I told you, it could be more or less, depending on how long can you last at this moment. The key is, take small steps and slowly go bigger.
I’d like to point out to read in a well lit, quiet place. Noice will distract you, and reading in the dark will damage your eyes that are already being strained by reading.

Hope this helps.

Try using an e-reader and make the print size quite large. Often people’s eyes get tired moving along the line. If the line is shorter, this makes it easier to read.

Can you suggest some non fiction book for reading,which you have probably read yourself?I don’t usually like reading novels etc. but I think I should read them like a stamina increasing medicine.Because I suspense can keep me pushing to read more paras or even pages.

Have you considered glasses or a prescription change?
My eyes get tired if I force myself to read without glasses. But if I use a weak set of “cheaters” ,+1.00 diopters, from the dollar store or cheap pharmacy I can read much easier.

Probably the thing that is making you tired as you read is – believe it or not – misunderstood words. Many words can be figured out from context, and you may also think that you know some words, but you don’t really know them, or they can be used to convey alternate or secondary meanings that are not clear to you.

So my advice would be to keep a dictionary handy and use it often. When you find yourself getting sleepy, then look back just a little bit, sometimes a sentence or two, and usually not more than a paragraph earlier and find your misunderstood word. Look it up, read all of the definitions until you know it well, and then get back to your reading.

Looking up words will certainly slow your progress a bit, but you will learn the words that are there to transmit meaning to you, after all, so your comprehension will grow quickly. And you’ll be able to read for as long as you like.

I think it depends on what you are trying to read. Can you give us a clue of what you are trying to comprehend, reading?

I am with @LuckyGuy about the glasses.
When I was first tested, and tbe doctor saw how badly I needed glasses, he explained that if I didn’t wear them, not seeing clearly would make me drowsy. He said it would be worst with things like reading, or working with my hands on small things. I find that to be true.
I also like to enlarge the print wben I can, and if I am using a reader where I can choose different colors, I find that helps.

You have the enthusiasm to pursue reading, and you say taking breaks helps. To me it sounds like you need to have your eyes checked.
If you cannot afford glasses, there are various organizations which take donated glasses from people when they have their prescription changed so they can be available for someone else to use.
I applaud you for trying hard to stick with your reading.

@Patty_Melt I got my eyes checked recently but my eyesight was fine.
When I make the text bigger on an e-reader,it makes me tired more easily because it gives the illusion that I have read a lot of length.And I have a dictionary in my cell phone and while reading,I look up any unfamiliar words on the go.I am not talking about any specific reading material.It’s the problem I face with almost every readable material like articles etc.

Try this; read some books with very short chapters. Make it a rule for yourself you will close the book to go do something at the end of every single chapter. No exceptions. Go to the bathroom, or pour a beverage, or make a sandwich, or feed your pet, or dust a room.
I bet after a couple of books, your reading will change.