My girlfriend and i had sex 4 days ago and yesterday she started spotting. she has cramps as well. is it to soon to be having implantation bleeding?

Yes: Implantation bleeding usually occurs 6-12 days(average=9) after ovulation. Assuming you didn't have sex within the the 6-12 day period prior to yesterday it would be too soon for implantation bleeding from sex 4 days ago, because it takes 5-6 days for the egg to get to the uterus and another 2-3 days to implant itself.

Possible: this may be implantation bleeding, though its probably too early for a positive pregnancy test.