Hi!
About "pak" may be you were confused by the existence of пак and пък.
-> пак = again (one more time, something that is repeated). It's synonym is отново;
-> пък = and/but/again/punk/gee. Depending on the context I think those are the possibilities of translation. Certainly there is possibility one to be missed. Note that here we don't have the pattern of пак with something that is repeated, rather a common word, used in the speakable bulgarian language, which is a conjunction or a particle and has as it's target to indicate a differentiation, a contradistinction or strengthening of a negation or a question.
In bulgarian пък substitudes а and но, which we can translate respectively as and/while and but/only/yet. This doesn't mean all of them would sound good in english. Here are some examples:
1. Аз ще чистя, пък ти ще пазаруваш - I'll do the cleaning, and you'll do the shopping. It could be Аз ще чистя, а пък/а ти ще пазаруваш;
2. Няма пък! - No!/No way!/I won't!/I wouldn't (for an example when a mulish person won't do something just because, he says "Няма пък");
3. Дали пък да не дойда? - literally: If I come?/How about I come => meaning: Isn't it better for me to come? (I can't translate this directly simply because I don't think there is a suitable expression in english. If anyone knows please say ). Here пък gives this nuance of isn't it better. Otherwise (Дали да не дойда?) I am just asking my self if to come or not to come. But when we have пък it transforms that meaning to isn't it better...