I COMPLETELY agree with a lot of what painted mouse said but do disagree with the handwriting component. Actually, a lot of children with dyslexia and other language learning disabilities also have fine motor difficulties, especially associated with handwriting. There are various reasons why this is and I won't get to technical as it could quickly become a twenty page paper. A lot of students I work with have weaker fine motor skills and in addition to receiving extra help in their classes through special education or modifications within the classroom, they need occupational therapy to strengthen their weaker fine motor skills. Some of these students have pain when they write due to their pencil/pen grip. This needs to be relearned. I can get into the reasons why a lot of these individuals have a tighter pencil grip but it will take a little longer to explain. In addition, it takes a lot longer for people with dyslexia to write the correct letter formation and to form a sentence. Often times dyslexia goes hand in hand with language learning disabilities.
When your ability to read and understand English improves, so does your writing. Usually when handwriting continues to be difficult due to pain or just the length of time it may take someone to write, I recommend a computer. Since you have difficulties using a computer, I question if dyslexia is the only thing you are experiencing. Has Dyspraxia ever been considered?? Perhaps you do have some other issues going on that goes hand and hand with your dyslexia diagnosis.
I still can't write one sentence with a paper and pencil with out feeling pain. I have compensated by the use of a computer. When I do have to write with a paper and pencil, I use a different grip taught by an occupational therapist and a special pen. Have you seen an occupational therapist. Perhaps they can assist you.
It is true that we have to work a lot harder than the average person. I believe I have beaten my learning disability by reading and studying English a lot more than most people. It has been grueling but well worth it. Yes, diagramming sentences is an excellent idea as well. It helps reorganize your brain and teaches you the correct order. I personally didn't "see" letters backwards but I often got confused with sentence order.
I am a school psychologist and am dyslexic. I attended mostly an all Deaf institution for graduate school and all my classes were in sign language. When I learned sign language, my written language skills increased ten-fold. My expressive language skills greatly improved as well. People who have dyslexia often have difficulty coming up with the right word and have an overall difficulty expressing what they know. The great thing about sign language is if you are having difficulty coming up with a word, once you sign it, the verbal word seems to come to mind...at least that happened with me. It's amazing. I really want to go back and do some research in this area. When I became practically fluent in American Sign Language, I didn't really seem to struggle with written expression anymore. My expressive language skills are still sluggish but they are much better if I am able to sign at the same time ( which would be consider pidgin sign language, not ASL). Unfortunately, it would look a little funny at my job if I am signing while trying to explain a concept to my colleagues or while working with parents.