Went through something similar. After many issues with side effects to osteoporosis drugs, I decided to try HRT. I did tons of research, as I was 15 years past menopause, but since I was in very good health, my doctor agreed the benefit outweighed the risks.
I was started on the estrogen patch, progesterone pill and vaginal estrogen.
A few weeks in I started to get severe acid reflux and worse I began having lightheadedness that had me feeling like I was going to pass out. In addition, I was experiencing heart racing multiple times per day.
My cardiologist ordered a heart monitor. My gynecologist suggested I stop the progesterone temporarily, as that can cause the acid reflux and the lightheadedness. That worked as those symptoms stopped almost immediately. But the heart racing continued to get worse. This showed on the heart monitor, but thankfully nothing more serious was going on.
In the end I decided to stop the HRT as it was impacting my life too much. Had I decided to stay with the estrogen my gynecologist was going to use a progesterone ring, as it doesn’t cause the same side effects as the oral pill but still gives you the uterine protection.
I hope things are able to work out for you, it’s all so concerning and frustrating at the same time.