Sternum pain. Like, what should i do.

Hi from around 2 days, I have pain around my sternum area, it sometimes feel like twitch and then feels like something is moving. Did a new stretching exercise that day if related anyhow. I also feel very tight around that area and sometimes when I eat, I feel more pain there. When I lay down to sleep, the pain increases alot and feels like liquid from stomach has come back to the throat. I am taking antacids after every meal and drinking water frequently but pain is recurring and also feel weak in my legs for few moments.  History-I get slight pain sometimes on the right side below my breast from around an year, not sure if the current pain is anyway related to that. Doctor gave me anxiety medicines for headache and other problems for sometime. My ECG, thyroid profile, chest xray were all normal around 6 months ago, now confused if this pain is related to any physical activity, anxiety, stomach problem or anything else. Kindly suggest what the problem looks like, what should I do.