"Are there any stds out there that can develop in a person without having sexual contact at all, and then spread it to others through sexual contact?"
The answer is NO.
STDs are caused by microorganisms - bacteria or viruses - and we have to "catch" them from someone else to get an STD, these microorganisms cannot be created in our healthy bodies just out of nowhere.
The scientific question of "how did the first person acquire it?" or "how was the first bacteria of STD born?" is quite a complicated question - similar to the origin of species, it is connected to the whole process of evolution of spieces, mutations and so on and today´s species, including microorganisms, are the result of billions of years of biological evolution and processes related to it.
But an std has got to start from somewhere. Scientifically speaking, how did the first person that got an STD acquire it, before that person start spreading it to others, causing an epidemic of stds we have today.
Are there any stds out there that can develop in a person without having sexual contact at all, and then spread it to others through sexual contact?
the pull out method is NOT a good form of b/c. plenty of women have gotten pregnant this way.
don't rely on the pull-out method :)
If two partners are clean, there is no chance for an STD. STDs cannot develop through the act of sexual intercourse alone. They are caused by viruses or bacteria which can be transmitted only by a person who is infected. So if you have sex with your monogamous boyfriend who has no STD, you cannot get an STD, so condoms are useless here - with regard to prevention from STDs.
As for pregnancy, it can be a little bit more complicated as the pull-out technique is not 100 % safe, e.g. there are some sperms also in his pre-ejaculatory fluids which can appear also before ejaculation.
But in your case as you described it, you do not have to worry about STDs in case of unprotected sex with your partner.