Context, context, context!
I take it that this sentence occurs within a longer narrative cast primarily in the past tense, and that the narrative transcribes or emulates oral delivery.
Oral narrative is marked by frequent shifts from the "base" past tense to present tense and back again. There are no "rules" governing when you should shift, or for how long—a phrase, a sentence, a paragraph, an episode—so all of these sentences are acceptable in this genre.
As a matter of narrative strategy, however, it's generally a Good Thing to have some sort of reason for any device you employ. (A fundamental rule in all the performing arts is "It doesn't matter what you do as long as it looks like you did it on purpose".) The typical purpose behind use of the present tense in a past-tense narrative is to make a specific passage more immediate and exciting. If that's your aim, then
- the first example makes the situation you found yourself in more immediate,
- the third example leaves that situation "inside" the narrative, and
- the middle example, where only "Next thing I know" is present-tensed, is a little odd—what you seem to want to make immediate is the abruptness with which the following state arose.
But that may not be your purpose at all. You may want to depict the speaker as an unskilful narrator or one who composes his thoughts out of scraps of literary cliché; or "next thing I know" may be a characteristic catch-phrase with which he routinely marks his climaxes. In any of these cases (and others you can imagine), the middle example would be entirely appropriate.
