You said your hair is thick,too. You may have as simple a problem as not rinsing for long enough. Most people don't truly rinse their hair long enough. I cannot tell you how many clients I have taken back to the shampoo bowl and when I wet the hair it suds up. That comes from leftover shampoo in the hair. Thick hair is difficult to rinse completely. I have found shampooing over the tub, where you can monitor the color of the rinse water, helps. You then time it to see how long it takes your water to go clear, and then rinse that same amount of time in the shower. Shampoo residue can smell by the second day. The other solutions may help. but I always tell clients to try the simplest cure first-which would be making sure you get all of the shampoo and conditioner completely rinsed out.