Confused and a bit worried 😣

Its currently 6-7 days past the time that AF should have arrived. A week and a half ago I had extremely painful cramps that lasted about an hour which I just assumed AF was going to make an early arrival. Well still no AF but I've been having consistent cramping and weird feelings in my lower abdomen since last the Wednesday before this past Wednesday. It seems to be in my lower back by my hips with the odd pains right bellow my C-section scar accompanied with pulling almost shocking feelings between my belly button and inner lady bits. My legs are extremely achy as well as the entire rest of me I just feel pretty in the dumps right now 👎 ( I also had heavy amounts of white stretchy discharge that almost resembled a mucous plus but white with clear bits) ( also I have no STI's I was tested for them less than a month ago and I dont have a yeast infection) anyways so I go and buy a couple home tests, 1 taken 3 days late and one yesterday. (first response) they both came back negative and I am flabbergasted. My cycles are pretty regular ranging between 27-32 days. So I'm not in cycle day 38 with no sign of AF and sitting here with these negative tests. I'm 21 years old so I shouldn't be having any sort of pre menopause or anything like that. I have no history of cysts or evidence of them I'm not stressed but I do suffer from an anxiety disorder which has never affected my cycle (i do not take medication for it I work out when I start having an anxiety attack to stop them without meds) I have a GYNO appointment for the 22nd and don't know what to think until then. I'm just worried that I may actually not be pregnant and might have something wrong with me 😞 I am not obese or two thin. I'm maybe 5 pounds over my BMI . I've tried running through all the possible causes but I'm seriously drawing a blank and any advice / stories / suggestions would be greatly appreciated !