Itching is a very common symptom of a Hemorrhoid. Instead of Prep H, get some cotizone anti-itch cream, and you will get immediate relief. Prep H has never helped me with the itching, just shrinking the hemmorhoid and relieving the irritation.
Don't buy the Preparation H cream for itching, it doesn't work. I use Cortizone Plus, and any of these are found in the same area as Prep H. For a few days you may want to keep a tube (they're small) in your pocket and apply a few times a day or just as the itch starts. After a week or less the itching will go away, and then you won't need the cream. But keep it around in case it starts up again, which should be rarely. Also, it's pinworms that cause anal itching, they can be found easily at night, and nightime is is when the itch would be most intense. Plus, you would see them very easily in any BM's. They are very small and white. There are also over the counter meds for these, but I think yours is hemorrhoid related. Also, not to be crude, but always make sure your bottom is clean. Any feces left on the area can cause irritation and itching.
Have you ever had periods of diarrhea (especially at the time when having fissures)? Fissures occur in fungal infection but also in Crohn's disease...
Parasites often produce some mucus and are present with some bloating (not necessary though). Parasites may be one-cell organisms like Entameba histolytica or intestinal worms...
Hemorrhoids are still possible...