welcome to healthcare magic.
Erythromicin is a safe antibiotic & can be used in pregnancy
if it is required;as for cough
syrup & anti-allergic it depends on what is the drug used.The worry you are facing is whether you can keep this child as you have used medicines.My advice is better consult a Gynaecologist with the medicines i think she will give you advice regarding the baby &i hope the answer is positive so that you can have this baby.
wish you good health & good luck.