should I test again? Update

Tested again last night on CD 40. Yet another negative test. Brings even more sober feelings that the first. I fear that this is yet another really irregular month. Longest cyle has be 49 days. 
It concerns me that they are so different in lengths every month. Any ladies have advice on ttc with irregular af??
I am completely late for AF. Due 21st for it. Was supposed to be last day today if I had started on time. But still no period. I tested on the 21st and it was a bfn for sure. We are trying to convince. But I don't want to get hopeful and get another negative and be sad all over again this week. What do you ladies think. Could I be pregnant but really low levels of hormones???? Test again??? Wait longer??? Gah!! 
Thank you (: 
Sending baby dust to all