Hi, it takes variable period of time after discontinuation of depo provera for the cycles to resume regularly and ovulation to start. This would explain your missed periods with negative pregnancy
test. You can take hormonal
pills like Regesterone
to induce withdrawal bleeding and wait for regularisation of your cycles. However if you have sex without contraception
in the meantime, till your cycles resume ,you should always check for pregnancy if your periods are delayed by 7 or more days and act accordingly.