So confused!

Almost 3 weeks ago I had random, 24 hourish spotting, which is totally unusual for me, I have always had a regular period since I first got my period. I looked online and it said it could be implantation bleeding. Since then, I've been nauseous everyday thru out the day (more so after I eat), light to moderate cramping, headaches, random dizziness when I stand up sometimes, back pain, tiredness, more frequent urination (that one is hard to gage since I drink a lot of water anyway), loss of energy, mood swings, gassy and excessive burping, vaginal discharge and now 3 days late on my period but all negative tests. No clue what is going on with me?!