Should I be concerned about pregnancy?

Should I be concerned about pregnancy? My boyfriend and I were fooling around and he fingered me. He had touched himself but never ejaculated. I made him wash his hands between touching himself and fingering me. Yet I still can't remember if I had him do this every time. My concern is that there may have been precum on his hands when he fingered me. Should I be worried about being pregnant? This happened on June 18 and my period shouldn't start until July 11...