Hey Cloud,
Did you take a trigger injection just before (well up to ~48 hours before) your turkey basting (IUI)? If so then rumour is (from the clinic) that some of this could still be in your system before the 14/15 days test day, which is why they advise against it. I have to say, I have had the trigger injection on all of my rounds of IUI and may perhaps still have tested a day or two early LOL. 2 weeks is a very long time to wait. Even with my successful cycle I only had a very feint line when I did the test on day 14. But it got stronger as the days passed. My clinic told me to wait a week and do another test, but who has the willpower to wait that long? I certainly don't! You can also get ClearBlue or FirstResponse tests (on offer in Asda a week or so ago) which can give you a result a few days before your period is due. I don't think a false positive is massively common, but clearly it can happen. I've never had one myself but that doesn't really mean anything! 
One thing I found helpful (for me at least) during the 2WW was writing a list of all the things I was going to do if I got a negative preg test result (like drinking red wine, eating medium rare steak, etc etc). I found that helped to ease the pain a little. Slightly foolishly though (so it later appears to me), I did not write such a list for what I'd do if it was a positive result. So I tested, got a BFP (Big Fat Positive) and then felt a bit lost not knowing what to do. Stupid, I know!
Yes, I've done back to back cycles using donor sperm but my clinic (Bourn Hall near Cambridge) sets aside 5 vials for your use up front so it's fine till they run out. Kwik - Isn't LWC your clinic or am I getting people muddled up?
And yes, the hormones screw you up. Depends on the strength you're being given (I was only on the lowest dose) but I still felt pre-menstrual mood wise a lot of the time. You will be more emotional, but that's fine. Just know it when you see it and recognise it for being the hormones.
So, caffeine - I think basically they recommend no more than 200 mg a day. Which basically means you can get away with 1 real filter coffee or 2 instant coffees (check online as my calculations there might not be right). I found this one a bummer, but have found some really good fake (decaf) coffees. I even survived 5 days in Italy during my 2WW with only decaf coffee (lots of places did it but not all, and I'm pretty sure I accidentally got at least 1 full caff coffee there). Most good coffee shops and restaurants do decaf, and you can get some good filter stuff from most supermarkets. Even Dolci Gusto/Tassimo do decaf pods which taste OK. Handily my work does not do decaf so I've been on fairly sh*tty decaf instant here. That said if I could be bothered to get off my lazy ass and wander over the road to the other 1/2 of our site I could get a decent decaf coffee from their coffee shop. After getting my BFP I have actually not really fancied coffee much. Weird.
Gosh, I've written an essay - sorry. I'd best get back to work! 
TD x