Letoval is the brand name. It contains an anti-cancer drug called letrozole, which is used in the treatment of breast cancer in post-menopausal women only (i.e. women whose menstrual periods have stopped). There is not a single country (except India) in the world where it is allowed to be used for female sub fertility. Letrozole is contraindicated (not permitted to be used) in young pre-menopausal women. Both, the Canadian drug regulator and the innovator company of letrozole Novartis, have warned gynaecologists all over the world not to try to use it for female infertility. Research on 150 pregnancies has shown that babies born to mothers who had consumed letrozole to increase fertility have suffered from bone malformations, cardiac stenosis and cancers.
Duphaston (dydrogesterone) is a progesterone to be used only when there is proven, documented deficiency of this hormone on the basis of blood tests. Unfortunately some drug companies are actively and aggressively promoting the use of letrozole and progesterone as if they are pregnancy tonics. Headache and stomach disturbances are well known side effects of Letoval. Other side effects are Musculo-skeletal pain, fatigue, dyspnoea, cough, rash, angioedema, chest pain, viral infection, vaginal bleeding, acne, hot flushes, abdominal pain, hair thinning. Vertigo. Weight increase. Ovarian tumours. Liver cancer. Ovarian hyperplasia. Sexual inactivity. Atrophy of the reproductive tract. Hypertension. Thrombosis (clot formation in the blood), pulmonary embolism (blood clots in the lungs), myocardial infarction (heart attack), angina, stroke, hemiparesis (paralysis). Cerebrovascular events. Dizziness. Increased sweating. Hypercalcaemia (high calcium levelin blood), pleural effusion (water secretions from lungs) etc. etc.
Hopefully as the time passes and effect of medicine is reduced you will get better. There is no treatment to get rid of side effects.