What may cause stabbing sternum pain, faintness, bloated belly and gas?

A lot of symptoms! Substernal discomfort of any kind is not to be ignored--its a warning sign that something may be wrong inside your chest. Please see my many healthtap answers on the subject of what causes chest ; abdominal pains. Not all such problems are serious, but you don't want to miss the problem that is. Your constellation of symptoms may or may not be related. Get checked please.