I had the lower back pain in the early weeks of my pregnancy and I didn't feel sick once for the whole nine months. As for the breast pain I too got really sore around the nipples kind of like a really hot feeling.
I didn't really feel pregnant until I had my first scan at twelve weeks and saw my baby on the screen (more like a peanut shape) but none the less a baby and I really felt pregnant when he started kicking which isn't until the 22nd - 25th week of pregnancy.
As for tummy firmness your baby is only 10mm if you are only 7 weeks pregnant so I wouldn't worry about that in fact enjoy the flat tummy while you can!
All your symptoms and non symptoms seem completely normal to me and remember every pregnancy is different.
I hope this helps.