STD or STI

What is the difference between the two?  Also, this is embarrasing but can a person get "trick" from having sex in the anal then putting it in the vagina? could he have been a carrier for years and not know it and if so why is it just affecting me and we have been together for 5 years with no other partners? Thank you.

[gracefromHHP]

Please keep all your questions in the same thread. You now have several posts going on and it gets confusing.

std and sti are the same thing. sti is the prefered term but most of us still just keep saying std out of habit.  

grace