Annoyed doesn't describe how I'm feeling right now! xD
So when I last played my guitar a couple of weeks ago, I noticed that the B and high E strings were both a little quieter than the others. At first, I thought it was the height of the pickups as I had a similar problem with my bass a while ago. I didn't mess with it anyway, because I can't trust myself, and that guitar is my pride and joy lol :L

But yeah, after that, the string snapped, so I hadn't played it for a couple of weeks because I hadn't got round to buying some new strings. So when I strung it up today, I noticed the problem was happening again, but only on the bridge pickup. So I tested each setting and found the other two to be fine, but it's just the bridge setting that keeps either being slightly quieter and staticy or it'll cut out.

I haven't got a clue about fixing electric wires or anything like that, but has anyone had this problem before?
I've never had a problem with my guitar until now.

I'm using a PRS SE Orianthi with a PRS Design SE HFS Treble Pickup in the bridge and a PRS Designed Vintage Bass Pickup in the neck.
Most likely just a loose connection in one of the bridge pup's wires. Since you don't have a clue about electronics, I wouldn't start learning by messing with a PRS Orianthi. I'd reccomend taking it in to a guitar shop and have them assess and fix it. However, you will want to eventually learn how to change pickups on your own. But like I said, I would never try to fix something that I don't know about on my pride and joy guitar.
Yeah, I had a feeling it might be that to be honest, but I didn't wanna mess with it. However, somebody suggested that it might be a dodgy switch? I'm not quite sure what's going on with it, but I just don't want it to cost me a bomb to fix since I'm broke :L
What causes the connection to become loose?
Poor soldering is your most likely culprit. I'd expect more from PRS but as it is an SE (nothing wrong with that as long as it plays good to you) and those are lower end and don't get as much critical attention in the factory. I'm not exactly sure what you mean by a "dodgy" switch, but it is most likely not the switch's fault. I'll try to look up the Orianthis wiring diagram to help you out (as I have nothing to do today.) As for the price it may be anywhere from $20-40. If it's only one wire then it shouldn't be too much of a problem, but if the entire pickup is whack, then you should probably get a new one.