PCOS and depo provera

I am 23 and I have pcos recently got sexually active and I went on depo shot to be safe from my side as my partner prefers to do it without condoms and has came few times ... I'm not planning for any babies till 6 years lol my periods have always been 3 times a year ... :/ 
So are my chances of pregnancy low - none while having pcos + BIrth control???