When should I ovulate?

Took this today at 6:30pm I know it’s negative but is there any way to tell when I should ovulate? I had my last depo injection aug 2017. No period until this month (7th) was on until the 13th. I hope I ovulate soon. Ttc!!! Been having slight brown / pink blood when I wipe the past day or so too so no idea what that is??? Any help greatly appreciated

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