Pauses, which always come between intonational phrases (IPs), are indicated by double vertical bars within the IPA system:
For a short pause between IPs, a single vertical bar is used:
Notice that there are no commas, full stops, question marks or ellipses used within the IPA system. Any symbols used in orthographic punctuation which are also used as diacritics in IPA have a completely different meaning within the IPA system. So, for example, an apostrophe would indicate an ejective consonant, a full stop (if used) would indicate a syllable boundary and so forth.
For a full IPA chart see here: International Phonetic Association Website. On the right, under the vowel quadrilateral, you will see the section SUPRASEGMENTALS. Notice, there, the single and double vertical bars used for pauses. Notice also the absence of any commas, full stops or ellipses to indicate pauses.
One last thing, for two Intonational Phrases with (virtually) no pause between them, use a single bar with a tie symbol (also under suprasegmentals on the chart) over the top:
For the Original Poster’s needs, then:
/ ˈdæd ‖ aɪm ˈstɪl ˈkipɪŋ jər ˈsikrət ‖ oʊˈkeɪ /
Note: The International Clinical Phonetics and Linguistics Association have their own, non-IPA extensions to the IPA alphabet for the transcription of speech by people with speech disorders (or, more correctly, the transcription of disordered speech). A significant proportion of these symbols are actually symbols already used in the IPA system. Others, however, are not and are specifically useful for the transcription of disordered speech. The latter are not part of the IPA system, and these are not appropriate to use in a regular language-specific phonemic transcription system, such as required by the Original Poster here. Indeed, they will often have completely different meanings in such a context.