I had sex a week and 5 days ago. im having signs of pregnancy. Could I be pregnant?

my breast are sore and my nipples are sore. I feel sick different time of the day. cramping in my lower back and in my lower belly and under my chest.

You might be. I'd read all three pages of the WebMD pregnacy symptoms (link below) and then decide if there's enough evidence for a test.

http://www.webmd.com/baby/guide/pregnancy-am-i-pregnant

you could just be about to start your period too. I was worried about the same thing and it was just my period that was late. but you can take an early pregnancy test depending on when your last period was.

What's are signs of pregnancy you have, check your signs as here:
Light headache
Dizziness and tiredness
Craving for food and gain weight
Aversion to foods
Heartburn
Feel hotter
Lower back pain
Strain lower abdomen
Constant urination
Swollen breast
Darkening areolas
Missed period
Nausea and sick every morning
source: http://howtoknowifyouarepregnant.org/