Dry humped w no clothes on and sat on his lap. he ejaculated. i checked and none got on vagina. it spilled on him but could i be pregnant? periods usually regular but i am 4 days late?

With your description you should not be pregnant. But if in doubt about the episode get tested.

In order to get pregnant, sperm must be present to fertilize an egg released from the ovary at the time of ovulation. The most efficient way to do this is vaginal intercourse. Pregnancy would not be possible from the description of sexual activity that you have provided.