Brown spotting

Tamara

Last period was on the 4/08 to 11/08 had unprotected sex on the 12/08, 13/08, 17/08 and 29/08. Had light brown spotting on the 6/09 to 9/09 been getting cramps pretty much everyday since, slight nausea and headaches every now and then. Not sure when I ovulated as my periods are very irregular. Not sure when to do a test.