12 days late, negative test?

As of today I am 12 days late for my expected period, on the week of my period being due i had PMS and small cramping, and have had it on and off ever since. I took a test this morning (Clear blue rapid detection) and it was 100% a strong negative (to my relief). Would you say this is reliable to assume i’m not pregnant and my cycle is out of whack? As from time to time it seems to rearrange itself or be irregular, especially as i’ve been off the pill for only 2 months.I don’t feel “weird”, or “off” i just feel the same as i always do.