Opinions please?!

My period was due on the 18th (I have regular periods) I had intercourse on the 9th I had spotting on the 12th (only when I wiped) for about half the day with mild cramping, it is now the 21st and still have not had a period. I haven't taken a test yet simply because I'm nervous about seeing another negative test (been ttc for 9 months). Is there a possibility that I'm pregnant??