Originally Posted by omidonline

Grammatically speaking, you cannot use "Simple Past" tense in conditional sentences to refer to "Past Time."
In other words, the inclusion of a simple-past verb in the subordinate clause of conditional sentences normally implies an unreal reference to "The Present Time."
So far as my knowledge of English grammar in concerned, your sentence is best structured as:
"If I hadn't spent so many years studing English, I wouldn't be able to speak English fluently.