Before you come to the conclusion about an ulcer, you need to check a few other possible candidates for disease. The location of the problem, as you stated, was under the chest area. If you are also suffering from dysphagia along with this pain, then there is a possibility that you might be suffering from Gastro-Esophageal Reflux Disease or Achalasia. Both of these diseases are, in a way, opposites of each other but have such similar symptoms that one could be confused with another. GERD is a disease that develops because of chronic acidity. The stomach acid continuously comes into contact with the valve at the base of the food pipe called esophageal sphincter, destroying it, and leaving it open for the acid to rise into the food pipe or esophagus. Conversely, in Achalasia, the nerves that control the opening and closing of the esophageal sphincter stop working and keep the sphincter shut, sometimes not even allowing liquids to pass into the stomach. In both of these conditions, vomiting is common. The only way to distinguish one from the other is to have an endoscopy. Also, in Achalasia, you would not be able to swallow and you could spontaneously vomit while you are eating.
The drug that you are taking contains ranitidine hydrochloride and is used to suppress the production of stomach acid. If you indeed have an ulcer then this is indeed the medication that you should be taking. Just in case you have a case of gastritis, then you should also be taking a bismuth or bismol as an antibiotic treatment. However, doctors have stopped prescribing this medication because there is a more powerful acid inhibitor called a proton-pump inhibitor and this can be found in drugs like pantoprazole and omerprazole.
Assuming that you only have an ulcer, the first thing to do is to reduce acid production. Start by cutting the stress out of your life and eating frequent meals. This does not mean that you end up snacking more often but rather that you have some kind of fruits through the day, whether you are hungry or not. A glass of milk or some kind of dairy product like yoghurt after every meal will reduce the effect of high acidity as well. Additionally, you must also stop smoking and alcohol consumption until you are completely cured. Switch from your cup of coffee to having ginger tea instead as well.