Fibroids and polyps are almost always benign (~99%) so hysterectomy would be overkill. And hysterectomy causes lifelong harm. I call it the surgery that keeps on giving... problem after problem... even if the ovaries are "preserved."
Intercourse or pelvic exams can cause polyps to bleed. And if they aren't removed at the base, they can recur and cause heavy bleeding.
What were the reasons for the D&C's - as part of the polyp removal or was your lining too thick? If so, how thick? Imaging is not exact so fibroids and polyps can make the lining appear thicker than it is. And HRT can also cause a thicker lining. You don't want to have too many D&C's since that can cause Asherman's Syndrome and chronic pelvic pain.
HRT can cause spotting or bleeding. But it's also not unusual for women to experience some bleeding in the early post-meno years since the ovaries continue to produce hormones. Typically, it's nothing more than hormone surges versus something sinister. In my connections with other women on HRT, it seems bleeding is more apt to happen when they take micronized progesterone (e.g. Prometrium) versus one of the progestins. In this case, it may be better to "cycle" HRT versus taking it continuously. That would entail stopping the progesterone or progestin every so often (monthly , quarterly) which would force a bleed and keep your lining thinned out.
I had a hysterectomy 12 years ago and have connected with many other women who have and the large majority gravely regret it. Some women were in their 60's or 70's when they underwent surgery and have been severely affected by the after effects.
Sorry for the novel! I hope this helps.