I had a caesarean section on may 9th, I saw my period on the 12 of June then again about the second week in July, I have not seen my period for August. I took pregnancy tests and all came back negative, what could be wrong

Could be your system still getting back to normal. Not unusual for some irregular cycles in the beginning after childbirth. See what happens next month. If you are breastfeeding, or if you did even for a short time, that can also play a role.