I'm just gonna go ahead and echo what a few others have said here and advise you to start sanitizing. I see that you got some PBW and StarSan, so you're already on your way to better beer. Here are a few things that I think will help you get to your goal of your dream IPA.
Since your beers are getting funky within days, I would guess that you have some serious buildup on parts of your equipment. It doesn't take long to get buildup, either. My first infection was on my third batch, and I realized that I needed to fully disassemble all of my bottling equipment to properly clean it. That means disassembling everything that touched beer and soaking them in warm Oxi-Clean Free or PBW. The threads on your bottle bucket spigot and nut are prime locations for nasties to breed. The bottling wand valve is another danger zone and absolutely must be disassembled and cleaned, all the way down to the rubber O-ring on the valve tip. Remember: If it touches beer, clean it.
One item that I find to be excellent at cleaning all these narrow round spaces is a baby bottle nipple brush. That little brush is a serious cleaning multitasker. You can find them paired with full size baby bottle brushes, usually at the grocery store or Wal-Mart in the baby section. I stick mine anywhere it'll fit (har har), and I find the nylon bristles to be tough enough to get the gunk out, but not so stiff that they scratch and gouge plastic. I'm sure you've heard this before, but I feel like I spend more time and energy cleaning than I do brewing, and as far as actual "working time" (not waiting for mash conversion, between hop additions, etc), I'd say that's accurate. I think this is critical for good sanitation though, since a dirty surface is impossible to sanitize, and clean gear looks better and lasts longer.
You said that you briefly soaked your bottles in one step. If they were new, then that's probably fine. If they were reused, then a quick soak might not be enough to fully rid the surface of contaminates. The inside of your bottles should be spotless, especially since that's where your beer is going to be spending the majority of its life. Also, if you reuse bottles, you should definitely rinse and swirl with HOT water immediately after they are emptied. By making sure that all residual beer and yeast in the bottle is gone before drying and storing, you'll spend far less time and effort scrubbing when it's time to clean.
As for cleaning and scrubbing, a bottle brush from your homebrew shop should really be all you need. I have one of those big rope handled tubs from Wal-Mart that I fill partway with some Oxi-Clean Free and hot water. I soak my load of previously rinsed bottles for ten minutes or so, hit them with the brush, rinse, dry, and store. I can also get any remnants of labels or glue off of the outside at the same time if I need to. The bottles come out completely spotless and ready for beer, and it usually takes an hour or so from start to finish.
On bottle day, also remember to sanitize every bottle. I pour some sanitizer into a bottle, swirl it around every surface, then pour into the next one. Splitting the workload between two or more people makes this a five minute or less procedure. Alone, I'm looking at ten to twenty minutes. A vinator and bottle tree will make a solo job a five minute one, but it's also more equipment to clean, so I stick with my procedure.
Bottle caps can be pretty dirty, too, so toss those in some sanitizer for a short period before bottling.
Hoses are cheap and should be replaced every few batches or so, or once they start getting cloudy, discolored, or smelly.
One last thing, you said that you are using muslin bags to dry hop. Cotton is extremely porous and takes a long time to dry, which is what makes it a fantastic breeding ground for bacteria and yeast. I know it's *possible* to sanitize it by boiling and soaking in starsan, but It would probably be better to err on the side of caution and use a nylon hop sack. These can be found at your LHBS and from online shops, and are reusable.
I don't know if any of these steps will clear up your contamination problem, but they helped me, so I figured I'd pass them along. I went from a horribly infected, bottle fermented from 1.012 to 1.004 gusher batch to free and clean beer without replacing any of my equipment, just by cleaning more thoroughly.
Here's to clean beer, and your ideal IPA,
Good luck.
