I am 18 years old and looking to buy my first chastity belt. I have had this fetish for about two years now. I definitely don't want a waist belt, just something functional and discrete like the CB-2000, 3000, or 6000. I want to learn to wear it and eventually work my way up to wearing it 24/7, for upwards of 40 days at a time.

HOW DO YOU MEASURE YOURSELF FOR A CHASTITY BELT?
My penis is almost 5 inches long, and not too girthy (I haven't measured the circumference). I believe my package has a circumference of a little over 6 inches, but I could be wrong. What do I need to measure, if anything?

WHICH BELT SHOULD I GET?
I don't know which is the best of the three I mentioned, or if there's one brand I'm overlooking. I want something that will keep me from getting an erection, much less orgasming, and which will not be noticeable under clothing. I'd also like to spend less money if possible, but if not possible, fine. Plastic only, no metal, no waist belts.

WHERE SHOULD I BUY IT FROM?
I've looked at ExtremeRestraints, and that's about it. I'll go shopping around, but if anyone has good insight on this, let me know. And how do they ship it? It would be rather embarrassing if the package were labeled, considering I have to pick this up from the front desk of my college residence hall.

OVERVIEW
I'm pretty sure I want either the CB-2000, 3000, or 6000. I want plastic. I want it to be secure. I want it to be undetectable under clothing (even underwear, if possible?). I want it to be relatively inexpensive, functional, and easy to maintain.
I had a hard time choosing a category for this one. If someone could direct me to the correct category in which to place this, I will gladly re-post it there.

By the way, can someone explain to me what the Points of Intrigue are?