They mean slightly different things, dont they? The first means that you paused, then stammered, then reiterated the point. The second means that you paused, and then when you reiterated the point you stammered. So, both are right - which one you use depends on what you mean to say. I presume it is the second, because I dont know how you could pause (that is, stop speaking), then stammer, then begin speaking again.
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