Hi,
The depo can take ages to get out of system, flipping horrible contraceptive I found with constant periods that last forever . I got mine out ages ago and went straight onto pill which regulated me. It was a good couple of years between depo , pill and ttc but did fall the 1st months after coming off pill so maybe it reset my system.
BF will also have slowed ovulation down. If temping doesnt appeal you could buy some ebay chapie ov sticks and use them for a month and see where is gets you before visit to docs perhaps.
Good luck xx