6 and a half weeks pregnant with 3rd child and these symptoms are different?

Hi, im 6 1/2 weeks pregnant with my 3rd child, but these symptoms are really strange and different. My first was nothing, my 2nd i just had nausea a lot and running to the toilet, but this time around, im always hungry at least 2 hours after eating, and even then, im still starving! I get nausea if i don't eat and im already getting slight twinges in my mid/lower back on occasion and constant cat naps. I've read that these are signs of twins? As much as i desire to have twins, i want to know if other women have had these symptoms on their additional pregnancies?