Need some advice. I recently had intercourse with a girl and during it I stopped so not to take it to far. She slept with someone else 6 days later and he said he went all the way. She is now pregnant. She says her date of conception is between 23rd and the 27th of December. Now I admit we were together on the 26th. She slept with him on the 31st. My question is how accurate is the blood test? Also she says its mine but I know I didn't ejaculate. Can you get pregnant of pre ? Could she be lying cause she doesn't really like the other person?

Yes, pre-ejaculate contains sperm and can impregnate a woman. In this case, it is a toss up. The only truly accurate test is a DNA test. Pregnancy may not be the only problem because she evidently has no problem having unprotected sex with multiple partners. You should be tested for STD's as well as her too if the child is yours.