3 months and 18 days late for my period.

Im 19 years old and i have had this issue once before but it was only a month late that time this time its now been 3 months and 18 days and im stating to get concerned. Ive gained ten pounds and ive researched a lot of things saying weight can be a reason for it but im also very stressed and have constant panic attacks from stressing over this so much and because my girlfriend is visiting from california and that just stresses me out even more so maybe the two combined is whats doing this. i know its not prenancy because im not sexually active and i keep very clean in that area. I have discharge but its always clear with occasional milky looking particles mixed with it. I just need some kind of answer because stressing over cervical cancer at 19 isnt something that i should be so stressed about. HELP.