My boyfriend is the only person i had unprotected sex with and my std test came up positive and his came up negative. i got the treatment already..

STDs often are found: ...in only one person in a couple. They're not always transmitted. The tests aren't perfect, can give false results. Most STDs go away even without treatment, so bf's infection might have cleared before he was tested. Or he was treated but didn't tell you. Syphilis is only transmitted when early; maybe you're beyond that stage. If gonorrhea, chlamydia or syphilis, bf still needs treatment.