Pregnancy Question...Just Wondering?

How long should I wait to take a pregnancy test? My last period was October 18th, and while I am irregular, the last few months have been almost like clockwork...except for this month. My husband and I have been TTC #1 for almost 1 year now, with no luck unfortunately. So since my period is so irregular, I usually give it a few days to get here. I've been feeling very crampy and have had sore , but that is sort of normal PMS for me. Except the cramping this time is lasting longer than usual and coming and going. I don't want to build anything up in my head, so when (if I do not get my period soon) would be a good time to test? Oh and we did have unprotected about I'd say 3-4 days BEFORE my period was due (I cannot remember the exact date!) DO you think I have a good chance to have conceieved? When should I test? Thank you to all and *babydust*!