Hi thanks for your question.
One of most important cause of irregular period is hormonal
imbalance. It is treated with oral contraceptive pills
like Oral G. Your weight has increased from 76 to 80 Kg after start of Oral G. Yes this can occur as increase in weight is side effect of Oral G. Positrim is the brand name for ready to eat meal replacements in the form of nutritional balanced milk shakes and bars. Meal replacements are effective when used properly. There is no side effects of this nutritional replacement. You have take a balanced approach as on one hand you are taking medicine which increase weight and on other hand you want o reduce weight with positrim.
Hope this answers your question.