welcome to health care magic.
does happen in early pregnancy
. some women experience it a little more than others. you said the colour is black sometimes, is there any blood? please do check that properly. you can take some antacid
syrup, mucane gel, eno fruit salt. eat small frequent meals. drink plenty of fluids,take juice,coconut water. strat with small sips. do not worry,all these symptoms will subside once you are in your second trimester (after 12-13 weeks). also try to have some rusk biscuit in the morning as u wake up. completely stop tea and coffee. if u still dont fell better,then better u go n see a gynaecologist.