weird... my hair started thinning very noticeably when i was in china, too. (i'm f, late 30s, was living in rural china). i'm also vegetarian, and found it difficult to get well-rounded nutrition in the area where i was living.
a couple ideas:
a. maybe cut down on the soy a bit. soy has phytoestrogens, so i wonder if this might be causing a hormonal imbalance if you are eating a lot of it. note that there is absolutely no evidence, to my knowledge, linking soy with hair loss, but this might be something to try.
b. i don't think that there is any evidence that sls is linked to hair loss (someone please correct me if i'm wrong.) sls *can* be somewhat drying and thus contribute to breakage, it doesn't degrade in the environment very well, and some think that it fades hair dye more quickly than some other similar ingredients, though.
c. when i saw a dermatologist about hair thinning, he recommended not dyeing my hair, or at least making sure that the dye did not touch my scalp. i hadn't dyed my hair for some years, so i don't know if this helps.
d. are you using a blowdryer? it's common to use one in the parts of china where the indoor heating in winter is inadequate. the dermatologist recommended not using a blowdryer. apparently, the heat from the blowdryer might not be great for hair follicles. if you need to blowdry, use the cool setting only.
e. is it possible that your propecia is fake? my chinese friends told me that about 90% of the western medicine in china is fake because there is such a high profit margin on it. although it seems unlikely that an indian-made version of propecia would be faked in china, i'm always astounded at just how rampant the pirating is in china -- as you are, too, clearly from your second paragraph. or is it possible that the medicine might have been exposed to too much sun and degraded, i.e., if you had it shipped in from abroad?
f. sometimes a high fever can trigger a temporary hair shed. since your shed sounds like it's ongoing, this may not be relevant, but i thought i'd add that in case you'd had an illness several months back.
g. definitely try biotin. my dermatologist recommended that to me, and it did help stop the shedding, though it didn't seem to help with regrowing. it's a vitamin; you generally have to buy it separately from a multi-vitamin. there are threads on it here at LHC.
h. that you're seeing regrowth is a very good sign. my understanding is that sometimes regrowth comes in very thin and fine, falls out, and then grows back more strongly.
i. you might try using an ayurvedic oil with bhringraj, brahmi, and/or amla. put a tablespoon or so on your scalp before going to sleep, put a towel over your pillow, and shampoo it out in the morning. one sheds a little bit more on the day one uses it, but i've found it to really help with regrowth. i use auromere, but henna sooq, better botanicals, dabur vatika, and other companies make similar products.