please help :(

my period is late by 9 days now...

its always been irreagular but this is the longest its taken to start.

i am somewhat sexually active, though i use protection everytime.

im not sure if i should bother with a test or wait longer. im having slight cramos like my period wants to start but nothing yet...

im not sure what to do

also to note; i recently had an allergic reaction and had to take new meds for 4 days. prednisone 20mg.