Do I need to use condoms if my boyfriend might have an STI and not know it?

If my partner and I have been monogamous for three years (and I was a virgin before we met) and my partner tested negative for the HIV virus (twice, about two years ago, with a six-month gap between the tests) is it safe for us to use a birth control method other than a condom? That is, are there still any STDs that my partner might have without knowing it, that we should be worried about, even though nothing whatsoever has seemed wrong with either of us for three years and my partner has had several regular annual physicals in that time?


What kind of lube should I use when I cock-stuff?

I have started "cock-stuffing" in the past year or so. I use a glass thermometer and insert it into my urethra. I know that this is wildly dangerous — as the glass could break — but I thought it safer as it is manufactured very smoothly.

I know other men who use a variety of implements — pens, markers, tubes, etc., but I have only done it a few times — and it seems that the glass — while not safe as it could break — is safer as it must surely be smoother.

I use my own saliva as a lube — as I am not sure if a personal lubricant — i.e., Wet, KY jelly, or the like, is safe. Not that putting a piece of glass into your urethra is all that safe to start with.

My question — in the end — is personal lube okay to use? Is this a common fetish — I don't do it often — and it doesn't seem to affect me adversely afterwards.

Thank you for any light you can shed on this.