Missing your period and then feeling sick and getting negative pregnancy tests is seriously the most frustrating thing ever. I've personally been there, and I know how infuriating and confusing it feels. It's like your body is playing tricks on you and then the anxiety of worrying if something else is wrong makes everything feel worse.
My best advice is first, you need to take a deep breath.
If you missed your period two weeks ago and you're still getting negative pregnancy tests then, except for the slim chance that you ovulated very late and it's still too early to get a positive pregnancy test, it doesn't sound like you're pregnant.
It sounds more like you have a delayed or missed period and your body is either getting ready to ovulate, getting ready to start that period (finally) or like you're dealing with a virus which could also be the cause of your missed period.
Going way, way back to our ancestors, our menstrual cycles revolved around conception. Back in the day when there were limited resources, our bodies would delay ovulation if an illness was coming on because we couldn't have sustained a pregnancy and an illness back then - there were no grocery stores, walk-in clinics or Gatorade.
That means that if you've been sick or stressed it's possible that this is the reason your period is so late, not pregnancy.
If you can, I think you should contact your doctor and let them know your symptoms and about your late period. They can give you a simple blood test to confirm whether or not you're pregnant.
In the meantime, hang in there - you're not the first, and you certainly won't be the last woman to feel sick with a late period and negative HPTs! This almost never indicates a serious issue.