You should say, "I had a car accident."
The present perfect tense is used in sentences like the following ones.
Mario has arrived home.
Michelle has shopped at that store since she was a child.
She has walked downtown everyday for a week.
The first sentence means that Mario arrived home, and he still is at home at the present time. (Suppose I say that sentence to a person who is listening me, now.)
The second sentence describes an action that started in the past, and continued into the present.
The third sentence describes an action that happened in the past, and that was repeated.
Since having an accident is an event that happened in the past, but that didn't continue into the present, nor is it an event that was repeated in the past, you should not use the present perfect.
Notice that British English and American English use the present perfect differently; in some cases, British English would use the present perfect tense where American English would use the simple past tense.
Might you ever have read is OK. It's asking if they already read it in the past (NOT still reading it). Might you ever had read and Might you ever have had read are both ungrammatical. If you need to know if they were in the process of still reading it, you could ask: "Might you have been reading that book when you fell asleep?" Or: "Might you ever have been reading that book when you would fall asleep?"
Best Answer
Both the constructions are correct. If you say
You can parse it as