Be glad you don't have many symptoms, because once you get them (if you get them) you'll wish they were gone. It's normal. I am 19 weeks with a healthy baby boy and only had symptoms 1 week out of the 19.
Yes sore nipples/breast are a good sign. You may even have hot flashes. Just don't worry too much, your symptoms will come and go, i didn't even get any this pregnancy until 8 weeks, i am now ten weeks And the only thing i have is very tired. With my daughter i was so sick starting at 4 months but nothing before that (didnt even know I was pregnant until i was into my second trimester) but with my son i had symptoms a week after i conceived.