Hi!
My suggestion is to simply pinch yourself at the beginning of each question (kidding... but kind of not!).
What I really mean is that it is fine to hesitate momentarily to think about what you are looking at, and to ask yourself "What have I learned about this? What traps can there be? What am I supposed to check?" AND to remind yourself: "I will not read the text or the answer choices too quickly."
Essentially, when you look at a question, such as Subject Verb Agreement, when you see a verb you should ask yourself where the subject is and what type of subject it is. By doing this, your mind will start running through all the different subject types there might be. Then you will ask yourself about the tense: "What is the tense used? Is it the right tense? Is there an indication that it should not be this tense?" etc.
For most people, 10%-15% of their errors are avoidable. Eventually, once the knowledge is in you and you know what to check without asking yourself the same questions each time, you will be able to notice rather than have to pause. But for now, train yourself to read carefully, to identify the question properly, and to notice the small differences among answer choices. (For example, why do "b" and "c" both sound good, and what is the difference between them-- because one is wrong?)
A slight pause and self-reminder to slow down may help you. It is OK to be pressed for time, however, looking at the clock after every question will not help. Nor does it help to rush through things. For now, simply try to remind yourself of what knowledge you are supposed to apply, and what you are supposed to check/identify. Focus on attacking the questions in as systematic manner as possible.
Kind regards,
Evan