I am 16 years old I have a baby but he's over a year old, and my vagina is very swollen and its burning and itchy, it happened to me before it keeps happening right when my period ends

Sounds like a yeast infection. Make an appointment with your doctor for proper diagnosis and treatment.

Last time I had a yeast infection I took medicine for it and it went away but then it came back and the same time as last time

Sometimes your partner needs to get treated as well.