Testing too soon? Pls Help! OPK

I started keto like 2 days ago to help with weight loss and TTC had AF on sept 10–14th it’s only only been 3 days but I was told by a lot of people to test right after period. Is this normal to show only a faint control line only since I am testing too soon? Is it really too soon? When should I test? (If I don’t take provera I don’t get a period) so I honestly don’t know when I am supposed to ovulate I try to take my pills monthly (31-34days)