I had sex last week can i be pregnant if ur back and stomach is hurting after unprotected sex from last week?

Of course, or worse: Of course you could be pregnant but the pain you describe may also be from a sexually transmitted disease like gonorrhea, a urinary tract infection, or even appendicitis or gallstones. Get to a doctor or go to the ed asap. Engaging in unprotected sex used to be a gamble but in today's world acquiring some form of std, becoming pregnant, or both should be expected if you don't use protection.