Had unprotected sex within 40 days of recovery after givin birth. four negative hpt. possibility to still be pregnant? when to test again?

Not pregnant, unless: Unless a woman is continuing to have unprotected sex, then she is not pregnant after getting 4 negative pregnancy tests (if the tests were done correctly and done 2-3 weeks after sex). If she continues unprotected sex, and cannot tell if she is pregnant, she can do a pregnancy test every 3-4 weeks (but doesn't need to if her regular periods come). If not wanting pregnancy, just use contraception.