When should I take a test?

I stopped taking the combined pill 4 weeks ago. I've been on it since I was 16 (13 years!) So have no idea about my regular cycle. We've been having regular sex since my withdrawal bleed, but as I don't know when I'd have a period, I don't know when I should be testing. I don't know my ovulation symptoms, so may not have even ovulated yet! I do have sore nipples (not breasts) but this is probably paranoia.

Any advice is greatly appreciated.