For constipation you could increase your intake of fluids, fruits and fibrous foods like oatmeal. There is something called Psyllium or isphagola husk that you can mix with water and take after meals at bed time. It is natural product. It happens to the most of us but things will get better.
Headaches can possibly occur because of the constipation and gas issues in your case. However, you can massage your forehead with the oil of viola odorata commonly called as Banafsha. It will help you with headaches.
About acidity you could use Root of Licorice. Note it can slightly raise your Bp if consumed more.
However, the biggest concern is the passive smoke you are exposing yourself to. I think you should ask the gentleman smoking next to you in a kind and loving tone that you have quit and want to say quit so please he could smoke without harming others and if he takes it lightly then you could say that you are suffering from some disease and the doctor has advised you to avoid smoke at all costs, so may be he has pity on you. Passive smoke is unacceptable but I think it is better to take the route of kindness rather than anger.
Anyways, you have done a great thing by choosing not to smoke. Stay put and dont loose hope,. This is a wonderful community and we are here to support you in your journey towards a better and healthy life for yourself as well as the people around you, your family, friends. take care!