Horribe sinus infection/flu but brown vaginal discharge on depo!?

Hi,I have been on depo for about nine months,this past week I have gotten a bad flu/ sinus infection,tonight I noticed some brown stuff on my knickers,I was sweating earlier in the day from cleaning,also I have been coughing so hard sometimes I pee a little (sorry lol) I'm 21 and havnt had a period since I started depo.is the discharge on my knickers related to my flu?

Actually now I look at it more close,I think it might be pee stains from my coughing