singular & plural

Your question is almost incoherent. I is the first person singular. If one wants to speak of more than one individual in the first person, we have the first person plural pronoun, we. Just so as not to confuse you, i won't discuss those few, rare examples in which one would say "I were." Suffice it to point out that we say "I was" because it is a singular pronoun and that's how the simple past of the verb to be is conjugated in English.