The best way to tell if your hair is thinning is to keep measuring your ponytail. Also start taking pictures of your hair and scalp, parting it in different areas. I would also suggest taking pictures of the shower drain (I know gross) to see how much you're losing in the shower. You basically have to keep a good hair journal and log everything.
From the products you are using I suspect you are US-based? I am now in Asia, so I'm using Renew Skincare Australia Everyday Purifying Shampoo. These are the ingredients:
Aqua, Cocoamidopropyl Betaine, Decyl Glucoside, PEG-150 Pentaerythrityl Tetrastearate, Polysorbate 20, Rosa Canina Fruit Oil (Rosehip), Hydrolized Wheat Protein, Lawsonia inermis (henna) extract, Arctium Lappa Extract (Burdock), Naturtinum oficinale (watercress) extract, Equisetum Arvense Extract (Horsetail), Urtica Dioica Extract (Nettle), Syzygium paniculata (lilly pilly) extract, Yucca Schidigera (yucca) extract, Santalum Spicatum (Australian Sandalwood) oil, Citrus Reticulata (Tangerine) Essential Oil, Vanilla Planifolia Extract, Macadamia Ternifolia (Macadamia) Oil, Simmondsia Chinesis (Jojoba) Seed Oil, Lecithin (soy), Persea Gratissima (Avocado) Oil, Sodium Hydroxymethylglycinate (vegetable), Citric Acid (pH balance) Citrus grandis (grapefruit seed) extract, Phenoxyethanol.
I've had no problems w/ this low-poo, other then that I find it a bit drying, which is why I switched to cowashing in the first place.
If you're US based, a very popular low-poo is SheaMoisture Moisture Retention Shampoo. I've never tried it, but when I go back (in about a month) I'll be sure to buy a bottle. It has good reviews.
You can also go to the "products" section of nc.com and search for low-poos and read reviews. I believe there are many low-poos now on the market.