You may take the tests any number of times (But you will pay the test fees every time!)
If you study seriously, then take the test twice, with a gap of 2 months.
If you made mistakes in the first test, you have another chance to improve.
Fortunately, most Univs take the BETTER of two scores, independently, to your benefit!
For example, if your scores are :
Test 1. Math .... 590 Reading ....600. Writing ...... 650.
Test 2. ..... 450 .... 660 .........500
The Univ will take your scores as Math- 590, Reading- 660, and Writing- 650.
Isn't that good for you?