Gf agreed to have sex, but's virgin. i went as slow as possible by using pinky finger first (lubed), but less than 1 cm in, she said it was very painful, and couldn't breath. how can we overcome this?

See comment: Since i don't know the circumstances ; her background, she may not be ready for sex..She may not be naturally lubricated, there may be a guilt element..She may have a "smaller than usual vagina with time things will improve.....In some girls the hymen is tighter and tougher..Perhaps a visit to a gynecologist would shed light on the issue.

Exam: I would suggest beginning with an exam to be sure there is not an anatomic problem then prolonged fondling and foreplay to assure arousal. Hope this helps.