12 days late

My period is 12 days late..I've had 2 negative tests..1 at 9 days late and another one yesterday.

So I totally skipped a period for October and have no idea why, I've had symptoms like some lower back pain and really sore nipples and my discharge has been really wattery but I've had no spotting or bleeding at all..this has never happened before and idk if I should make an appointment with my ob or not..has this happened to anyone else? Can you be pregnant and have it not show up on a home test until this late or later? Help meeee