Best topical cream I've found is
Calmoseptine ointment or a generic from Walgreens, their moisture barrier ointment. It'll be in the adult diaper aisle rather than with the usual hemorrhoid creams.
I discovered the stuff as a caregiver for elderly patients and, later, for my grandparents and mom. It's used to prevent bedsores and pressure sores with fragile older skin. But it's also a terrific hemorrhoid cream.
The reason it works so well is also why it's rarely stocked next to other hemorrhoid ointments: it uses zinc oxide, which is really difficult to clean out of underwear or chamois/pads on cycling shorts. Takes a little scrubbing with a sponge and straight application of Tide, Gain or Dawn detergent.
Most hemorrhoid ointments use glycerin as a base, which is water soluble and much easier to clean up... and far less effective.
It's 20% zinc oxide, with a small amount of menthol, aloe vera, mineral oil, paraffin, the usual stuff. It relieves pain without burning, and the astringents reduce swelling.
It's worth the little extra cleanup hassle for the more effective relief.
Besides that, ditto the advice to get professional medical care.
Regarding diet, that's entirely personal and individual. No way I could do a vegan diet if I wanted to avoid hemorrhoids. I cannot digest legumes even with digestive enzymes. Tried it for a year in 2018, following recommended dietary programs, and it was miserable, constant bloating, gas, on the toilet all day, and not getting nearly adequate nutrition. My docs -- primary, ortho, endocrinologist and immunologist --were fussing at me for lab work that was out of whack, dangerously low thyroid hormones, vitamin D, iron, hemoglobin, high indicators for chronic inflammation, premature osteopenia, etc. I tried to supplement with legume and other vegan protein powder mixes. Nothing was helping. My metabolism cannot get adequate nutrition from a vegan diet. Some people can, but research indicates people vary in genetic predisposition to diets.
I switched to a primarily carnivore diet for protein, and some carbs for hard workout sessions. I cut way back on most fruits and vegetables, other than for flavor and color. Suits my digestion and metabolism. Turns out I didn't need nearly the amount of fiber and empty filler that some dietary advice insists on. Being on the toilet half a dozen times a day crapping out excess fiber and indigestible residue is not the solution to hemorrhoids. With my current diet my elimination is regular and predictable, once a day in the morning after breakfast and coffee. Far fewer problems with hemorrhoids. The only trick with a primarily carnivore diet is to be sure to drink plenty of fluids and, once we've established a regular elimination schedule, stick with it. Delaying a few hours results in excess water being reclaimed in the colon, which can cause constipation and straining to eliminate.
Occasionally I'll vary my diet and consume more junk carbs like bread and buns with sandwiches and burgers, more fruits and veggies just for variety. But it often causes more digestion problems.
But that's me. With a little experimenting and keeping notes you'll find a diet that works best for you.