No period since depot injection - trying OPK

[Sw19911]

I had the depot injection 13 months ago and still no period.
I have been reading some people say you can still ovulate and fall pregnant so out of interest I have been trying ovulation kits.
Today I had a positive...anyone else had experience with this?
Could there be another reason for the surge or might I actually be ovulating??

It took just over a year for me to get a period. First couple were very light- I decided must be too much in my system still so didn't try to concieve.. I got pregnant 4 months later, miscarried but within a year of first period has a 2nd pregnancy that was successful...
I was late 30s
I wish you luck