I suggest that you get a pregnancy
test done first to rule this out.
If your clothes are getting tighter, it indicates that you are gaining weight. Better check your weight to know if there is any difference.
Another reason could be the bulimia nervosa
syndrome, where people eat and then feel bad about it and react to it with such stress
that it causes nausea
. maintain a diary of the food that you are eating and look at it after 1 month preferably sitting with your doctor.
The third reason may be simple eating of too much unhealthy food leading to indigestion
. Just try to change your diet, that is add fruits and vegetables especially in your breakfast and do not eat fried food or food with cheese and butter or oil. Exercise daily, especially tummy exercises and yoga. These usually relieve the symptoms.
Good to see that you are so vigilant about your health. You will get over this soon. Have a good day and thanks for using HCM.