All the factors like being overweight, hypothyroidism and possible PCOS can cause difficulty in getting pregnant. Hence weight loss which you are already trying will help to a great extent. Also proper treatment of the hypothyroidism will be necessary. A healthy diet, regular exercise and de-stressing will help.
The answer is based on information provided. Exact advice is not possible without a proper examination and investigations. You are requested to consult your Doctor. Take care and keep us posted.