What shame (disgrace) was Rachel referring to?
Rashi #1: The disgrace of potentially falling into the hands of Eisav. 1
Rashi #2: As long as she did not have a son, whenever anything went wrong in the house ('Who broke that plate?' 'Who ate the figs?)', the blame would automatically fall on her. But from now on, she could place the blame on Yakov's (sweet little) son.
Rashbam: The shame of being barren.
Seforno: She was referring to the embarrassment that she felt, due to the fact that Hashem had responded favorably to her sister's Tefilos but not to hers.
Bechor Shor: I will not be less than the [other] mothers. 2
Refer to 30:22:1:1. Oznayim la'Torah: Until now, word spread that Yakov would retain Le'ah, who was able to bear children, and divorce Rachel, who was barren, and Eisav would marry her - See Oznayim la'Torah who elaborates.
I.e. this is based on the coming verse, that Hashem will give to her another son.