Welcome to HCM,
Your symptoms suggest that you have hyperacidity
with some reflux which causes heart burn, as diarrhhea is mild you have to just take water and electrolytes which can be taken in the form of ORS (Oral rehydration fluid) or natural fluids like coconut water and butter milk.
You can take some antacid
and H2 blockers like Ranitidine
with antiemetics,but you can do so after consulting your treating doctor.
As cold milk reduces acidity but can lead to rebound symptoms.
could be due to your physiological condition,take adquate rest and continue to take your calcium and Iron supplementation.
Take lot of water and fresh fruits like Banana, Papaya, Apple all helps to avoid constipation
Take care every thing will improve with time,continue your ante natal exercises that means deep breathing exercises.