What is STI? Is it different from STD?

I am afraid an STI is more or less the same as having an STD. Chlamydia
Gonorrhoea, Trichomoniasis, Genital warts, Genital herpes, Pubic lice
Scabies and Syphilis are all STIs and require you to seek medical advice asap.

In pregnancy some or perhaps all can affect the baby to come. The use of a condom during sex protects against most of these infections so what sort of person has sex without such protection? You need to ask yourself this.