Idk if im pregnant

Hi everyone. Im 24 years old. I have had a heavy period since i start when i i was 12. It last about 5 days really heavy changing tampons every hour or so. I didn't get any cramps or feel anything. i always feel cramps and almost sick before i start my period. I was expecting my period Feb 13th. But didn't get it till feb 18th. Which its not unusual to be a few days late so i didnt think anything of it. I got it was very light. And a light pink the first few days. And not enough to feel a tampon. But then the 26th it started getting heavier and now dark red. It has been now 10 days and still bleeding. I  took two pregnancy test  at different times and came out negative. Im on the pill and we are protected.just strange to me and a little alarming. I have a doctor's appointment on Friday to see but just want to ask if its happened before to anyone or have answers.