What Could Cause Small, Ball-like Lumps Inside My Vagina That Appear Intermittently?

Hi, I am a women who 29 years old, and i have kid.
before 15 days i found out some thing like balls in my vagina (inside in the hole i thin)but it not showing every time. Some time coming out .
And i am regularly getting periods with in all 30 days and this month it was late 2 days .