Having an itchy butt at night is a classic sign of pinworms. Having low iron levels is also a sign of other parasites altho there can be other causes.
At this point you need to educate yourself to relieve some of your anxiety. Read everything you can about parasites. Start with googling Dr. Andreas Kalcker. Go to his old website and read his parasite PDF. It will help you a lot with pinworms.
You can also read the book " Healing the Symptoms Known as Autism by Kerri Rivera " which has lots of info on parasites. The more familiar you are with parasites, the less anxiety you should have.
Feeling things crawling all over you can be your central nervous system. Having your back break out can be hormonal or diet related.
Start with cleaning up your diet. Eat only organic and see what happens. As your diet and digestion improve, you will naturally start eliminating some parasites. You won't get rid of them entirely but good health will be an asset when you are able to start a protocol to eliminate them.
I would recommend that you not do anything to eliminate parasites until you can deal with what is in your toilet.