Period confusion

Ashleiy
Ttc for about 3 months now. My period is always very regular. I am 13 dpo and last month my period was early. 26 days and I am usually 29 days. I'm a little confused this month. I am having NO period symptoms. I usually have really bad cramps , break out etc. This month nothing. I did ovulate late this cycle. Cycle day 20. I am due for AF either today or tomorrow. But like I said. No symptoms. I always feel her coming. I broke down and took a pregnancy test at 12 dpo. Negative. So coulple questions. 
1. What could cause my period to fluctuate the past 2 months ? It has been regular for years now. And then in the past 2-3 months I was 29 days ,26 days and now I'm on cycle day 33 with no AF
 Anyone else deal with this ? Is this normal ? 
2. Could I possibly be pregnant even with the negative test a day ago ? My doctor does not seem concerned and said to wait a week and retest if I don't start ... But it's making me anxious 
Any advice would bchance appreciated :)