Thanks for your query.Genital herpes
is contracted only by sexual intercourse - oral, anal or vaginal.
the likelihood of acquiring it by fingering is very remote - unless he had an open lesion on his finger and touched your private parts with those secretions.
Very hypothetical indeed.
You have acquired it from your current partner - that is the only explanation.
however his being negative on bloodwork makes it even more complicated.
The only thing for sure is - it is transmitted by sexual contact or oral mouth to mouth kissing.