There is indeed a theoretical possibility , yes that the sperms may get transferred from your mouth to his and then him giving you an oral can transfer sperms into your reproductive tract , and if you happen to be in your fertile cycle and if the sperms transferred are not dead by then, you can get pregnant with the act.
Though milky white discharge may be an indication of a fungal infection and not pregnancy induced discharge per se. The best way to find out would be to perform a serum beta hcg test after a week of the sexual act to look for raised hcg levels , which if found to be raised would confirm pregnancy.
I hope i have answered your query in detail,
wishing you good health,
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