Is it possible im pregnant?

About three weeks ago i had unprotected sex but he pulled out. My period came along two days after only lasting 3 days. My normal is 5 days. After my short period i experienced cramping, and pink spotting in my underwares later turning brown. Now i feel fluttering on my lower left side of my belly. Im really tired and have headaches sometimes. My lower right side of my back aches. after i eat i sometimes feel nauseated. My Montgomery glands are more visible and you can see my viens more. there are white stretch marks on my breast and my nipples are a little sensitive. Can i be pregnant?