Vaginal Discharge. The brown is probably some aged blood in the mucous...It may be left over from the last period. It could be some irritation of the cervix. If the menses is otherwise normal then this may not need to be worried about.
No and yes. There are differences of opinion, but I usually count the 1st day of normal menstrual flow as the 1st day of a menstrual cycle.
Yes. It's blood.
I had unprotected sex 18d ago on my first day of period and took morning after pill right away. Now I'm ovulating and having brown discharge. Whatisit?
Reaction to pill. The brownish discharge is old blood and likely a reaction to morning after pill. Unprotected sex can lead to sexually t transmitted disease as well. That discharge is not typical but one can acquire diseases without symptoms. Use condoms for prevention. See a doctor about that.