Why am I bleeding? Tmi

My husband and I have been trying to get pregnant for 14 months now. Today is supposed to be my ovulation day...but I'm bleeding. Why? It's kind of this pinkish color. I've never been pregnant so I dont know what implantation looks like. My period isnt supposed to come for another 2 weeks but my last period only lasted 3 days. I've had a slight change in my physical activity and I am now running 2 miles a day and working out since I'm trying to enlist in the military in June. Could this be why I'm bleeding? If I am pregnant, what exercises and to what extent can I work out? (Yes ik I'd have to postpone enlisting if I am) I just highly doubt I'm pregnant because we've been trying so long