When was your last period due? Did you have any type of intercourse at all, even with a condom?
When I found out I was pregnant, my breasts weren't sore, so don't think that is a sign you aren't pregnant.
If you are just going by your boyfriend fingering you, then chances are you aren't pregnant, unless his hand was still covered in his sperm (didnt wash his hands or wipe them off). You might just be stressing out.
Here is some info I found for you =o)
"sperm can usually live up to seven days when they're in the cervical mucus of a woman's vagina. However, when they're not being nourished and protected by cervical mucus, vaginal secretions, the warmth and moisture of a man's urethra and reproductive tract, or other warm and moist conditions, they die anywhere between a half an hour to four hours.
If you've touched semen, it's a good idea to wash your hands, or at least wipe them off before touching the vulva or vagina."