This could total be possible. I had it on my thighs when I was in my 20s and I grew out of it or it just went away. Then I had it come back and when I went to the doc she told me to switch my shower soap to Basis and use nothing else, use only dye free detergent for my clothes, don't wear anything tight and avoid synthetic materials (100% cotton only), bath immediately after working out, sweating etc, and don't get in a public pool or jacuzzi for a long while (the jacuzzi she told me to never ever get in again unless it was my own). I did it and it went away and never came back.
Yes parasites cause problems for many people but it doesn't mean that is what is causing this for you.
I hope you have good results with your new doctor too.