Your periods are fairly regular according to you.
If the periods are late by 37 days, I presume you had your menses about 67 days ago. At this stage, if there is viable
pregnancy, the pregnancy test has to be positive.
The negative test at this stage indicates mainly :
1. You may not be pregnant and the delay in menses is due to some other, mostly hormonal cause for which you have to take your gynae doctors opinion.
2. You are pregnant but unfortunately the embryo is non viable for more than a week. You mention the history of cramps. If they are
uterine cramps, this diagnosis carries more weightage.
Ultrasonography may throw a light on the exact condition.
It is better you consult your
obgyn doctor for advice. Probably you might be prescribed oestrogen-
progesterone pills for few days and expect withdrawal bleeding after 4-8 days.