Am I pregnant or is something wrong?

I should have gotten my period the 19th/20th. Had a couple of symptoms during my 2 week waiting period. They have completely gone away now. Took multiple pregnancy test. All negative! I'm usually very on time. Never miss a period or late. I'm not stressing. I've read that stress can delay periods but everything in my life is pretty normal. I first thought that my hCG hormone was too low but I am now on CD 40. I took an ovulation test which was positive on August 6th which would have me at 18 DPO! Anyone had a similar case? Were you pregnant or was it due to something else! Please help! A girl is desperate! I also forgot to mention that last month I had a chemical pregnancy. Would this throw my period off in anyway?