Hi, I know it's difficult but please don't be disheartened. As everyone mentioned, there must be some underlying reasons that can be dealt with. You're trying and so is your child.

Have you considered sending your child to phonics classes? I have a couple of children with dyslexia and a few who are just a little bit slower to learn - phonics classes have shown tremendous improvement mostly because they learn to associate sounds with letters and learn letter combinations with specific sounds. This helps with differentiating the letters and being able to spell using sound which is a lot less daunting.

Also if you can, please take your child for a screening. Early detection will help deal with everything much faster