Red bumps on roof of mouth and sore throat, is this from an sti?

See Doctor: If by sti you mean a sexually transmitted infection like syphilis the answer is yes. However there are other things than can cause red lesions and a sore throat. Consult a dentist and a physician as soon as possible especially if you suspect having a sexally transmitted infection, get tested for HIV infection also. Avoid all sexual contact until ok by doctor.