I have been off dupo shot for a year and six month. I want to know why it's taking so long for me to get pregnant

It can take upwards of TWO years for your system to fully recover from the after effects of depo.

TO answer that you both would have to be tested at a fertility clinic to see if either of you has fertility issues...

It could be you, it could be him.. it could be both of you, it might even be neither of you and it's the luck of the draw.