Bp as in blood pressure? No, I'd not associate the two. 3 days after unprotected sex would be way too early to really experience any changes. However, that doesn't mean she's not pregnant. If you had unprotected sex, she'll need to test if she misses her next period. Or 2.5 weeks after you had unprotected sex is enough time to get an accurate result on a home pregnancy test. Symptoms up until then are really not meaningful in determine if pregnant or not. They are often attributable to other things so very hard to read. If she's not pregnant, consider condoms or she takes birth control pills to prevent. good luck