Worried..Quick Question

I've been trying to conceive for almost three years now. I got on depo June 11 of this year for the first time. I missed my appointment for the next one which would have been for August 23 or so. I haven't had a period since July, and it was a normal period. 6 this morning I woke up and there was drops of blood dripping now my leg on my way to the bathroom. I used the bathroom and wiped myself there was a little spot of blood on the tissue(a light pink). I went to the store and bought a pack of pads, and I haven't bled again. 
​Can anyone give me an insight as to what this could be? Or has this happened to anyone ttc?