Help! 7 days late!

I have been off BC since January and my husband and I have been TTC since then essentially. I'm 26 and my period has always showed up on time, never more than 1 day off. I'm now 7 days late and got another negative this AM. It scares me because I know irregular periods don't bode well for getting pregnant. So should I go see a doctor or continue to wait? We were also going to start doing OPKs this month. Can I just pretend to be cycle day 1 today and start those soon or is there no chance now that I would ovulate because I haven't had a period?