Mohsenafra
For a lot of test takers, the pressure of test day can dramatically affect performance. But what's the solution? Is it more practice problems and practice tests? With the kind of consistent performance improvement you had on practice tests, your problem is not knowledge of the content. (I'm assuming you used a combination of Manhattan, Official and Veritas tests so the tests are a fair reflection of your knowledge level).
The real problem is your in-test process. It's not resilient enough to withstand the pressure of a real GMAT test that 'counts'.
In the live test, you'll start to make mistakes that you don't make in practice tests: missing information in the prompt, forgetting what variable you're supposed to calculate or calculation errors (those are just a few examples).
To avoid those problems, you have follow a more diligent way of solving quant and verbal problems. With quant, you have to:
1) Read the question and identify possibilities of typical errors (that you tend to make)
2) Capture and preprocess all the information in the prompt, answer choices and (in the case of DS) the statements
3) Visualize the problem so you don't have to keep going back to the intentionally confusing wording of the original prompt
4) Systematically setup the equations / calculations that you need to complete
5) Execute the calculations efficiently using shortcuts, estimation and other critical tools
The more consistent your process is for each of those steps for EACH quant question, the more in control you'll be in the test and greater chance you'll avoid falling to traps and making mistakes that cause the big score drop that you experienced (from practice test to live test).
The exact same thing applies to verbal (although the process steps are different).
I'm happy to discuss in more detail if you'd like. Your ESR could help to identify the 'what' of your score drop (what question topics, formats and stages you had the most trouble with). But the real question is the 'why' -- why did have problems with those things (and it all comes back to gaps in your in-test process).