Periods after birth

I had a baby 21 weeks ago and since having him have only had 2 periods. This month my period is 20 days late (or would be if my periods had gone back to normal). I’ve had lots of watery discharge like I did when I was pregnant with my son however have done 2 tests (one 20 days ago and one today) and both were negative. Obviously I can’t really track my ovulation very well as my cycles aren’t back on track.

How long did it take for your periods to go back to normal after giving birth?