I guess my first question would be what do you mean "nearly"?  Assuming you are a male receiving a BBJ the risk of Chlamydia is really, really low.  It is higher for the receiver since Chlamydia lives easier in the genital area than in the mouth or throat area.

DATY without a barrier carries the same risks as a BBJ which again are pretty low so I am not sure what the logic is in restricting one and not the other.

I personally think you should do some research at the CDC website or maybe talk to a doctor about the pure risk versus likely risk.  They are not the same.

the common cold is an STD, as well as hundreds of other things that can be contracted by being intimate, or simply by being close.

Question: How do you "nearly" bring some chlamydia home? It either is, or it ain't.

With proper use of a condoms, and pretending condoms never fail, you still run the risk of crabs and scabies, both parasites and treatable.

You also run the risk of Herpes and HPV (genital warts) both incurable. The risk from Herpes isn't just from kissing or giving DATY.  It is transmitted from skin to skin contact so you can still get it in the area of your dangly bits, even with a condom on for BJ and intercourse.  

Of course, condoms do fail.
They can come off, they can break, and even when neither of those things happen there is still 3% failure rate.

On the plus side for you, during "insertive" sex, the one giving is always at less risk than the one receiving, so that's something.

My good friend Louis said that on his deathbed: