I am currently going through this exact same thing in my first trimester, the burning is so annoying! Have you tried having cold milk or curd? Let me know if you find anything else that works, because I am struggling too.
Yes, early pregnancy hormones can slow down your digestion and cause that stomach burning sensation. My mother-in-law used to give me cold milk or fennel water (saunf pani) to drink, which helped a lot. But if you have any severe pain or spotting, please go to your doctor immediately.
Yes, it is very common to feel stomach burning due to acidity in early pregnancy. Try having small meals and drink plenty of water to keep it calm. Do consult your gynac if you feel too much pain.
Yes, progesterone slows down digestion, causing acid reflux and burning. Don't skip meals or stay empty-stomach during work hours; keep dry biscuits with you. If it doesn't get better with lifestyle changes or is very severe, ask your gynac for safe antacids.