This context comes from the show "Euphoria"
"I was shooting dope before your mama's egg dropped."
1)drop an egg (Urban Dictionary definition)
To become aroused to the point that one spontaneously ovulates, regardless of time in one's menstrual cycle.
That dude is so handsome. He makes me so horny I could drop an egg.
Or maybe it's the ellipsis of this phrase:
2)dropping more eggs then the easter bunny
When a woman is having her period
Did you hook up last night? No she was dropping more eggs then the Easter bunny
Did he mean that "he was shooting dope before her mama had her first period?