Hi welcome to Health care magic forum. All the symptoms you are describing are only due to PRENATAL tablets containing high dose of vitamins
To many people these can cause gastric irritation, so stomach pain, and diarrhoea
, black stools due to iron , alternate by hard stools, headache may be due to gastric desturbance.
With your doctors advise you may use anti ulcerants to prevent gastric irritation if you want to continue the same medicine.
To conceive immediately you both partners should consult a gynacologist for quick result.
Wishing for a quick relief and immediate positive result ,And i thank you for calling.