With my current pregnancy I had cravings for Avacados before I found I was pregnant. And that craving is what made me take a pregnancy test . My other pregnancies cravings came after the morning sickness stopped. Every pregnancy is different though.
I craved white bread and salt....weird I know. That's what made me take test since I also craved that with the first :)
They can start at any time. With my first, i didnt crave until 16 weeks. 2nd, I ate tacos for 1 week straight when i was 4 weeks. 3rd, i craved pickles from day 1.
I'm almost 39 weeks and still waiting for the cravings! I did eat more carbs in my first trimester though, but I wouldn't consider that a craving..I think it was just to help with the nausea. Good luck!
I'm 23 weeks and have not had cravings for anything in particular.