Avoiding pregnancy

Damini
Hi.
I am a 20 yr old girl and my menstruation cycle is irregular.i missed my periods dis month n i was about to get my periods on 2 march but its 15th. 
I have pelvic pain n mood swings n white discharge. 
I did a pregnancy test which was negative.
I am really tensed and stressed.. 
Help if u have any knowledge regarding it. 
Thank u