Please, try to talk with your doctor.
You mustn't stop taking methyldopa without consulting your doctor, because abruptly stopping methyldopa may increase blood pressure and cause unwanted side effects.
Yes, upset stomach and vomiting are side effects of methyldopa.
Methyldopa has not been studied in pregnant women in the first and second trimesters (the first 6 months of pregnancy). Studies in pregnant women during the third trimester (the last 3 months of pregnancy) have not shown that methyldopa causes birth defects or other problems.
However, every medicine taken during first trimester of pregnancy has potential risks for growth and development of the fetus.
When did you discover that you have problems with your blood pressure for the first time?