How early can implantation bleeding occur?

So I had my cycle start 1st November until 5th December as expected it was all fine. Then I had my ovulation week the following week 12th being my day. Monday 14th November I then had what seemed like another cycle occur lasted until the Thursday gradually getting lighter towards the end of the week.

I was on depo injection stopped this time last year 4th October was my first cycle after all that time was such a relief was going out of my mind. So 1st November I was due my 2nd cycle which occured as planned.

What can this random 2nd cycle like be it's so frustrating took us 2 years to conceive my daughter 4 years ago I can't go through that pain and disappointment again waiting was stressful :(

Any ideas or advice ladies please?