The only way to know for sure if you have bed bugs, is to produce an actual sample of the bug itself. Do not automatically assume that any bite-like mark is a bed bug bite. Also it is important to realize that medical professionals cannot give a positive diagnosis simply by examining bite symptoms, they can only suggest some possible explanations for what may have caused the bites/symptoms to occur. Obviously if you see bugs in your home associated with your bedding or other furniture, you should have it examined by a professional that is qualified to provide a positive identification. However, if you are experiencing bites but have not seen any bugs, you should consider the circumstances in which the bites are occurring. For example, there is a very good chance that you have bed bugs if you keep repeatedly waking up each morning with bite symptoms on your body that were not present when you went to sleep. A situation like this would be a good reason to have a pest management professional perform an inspection to identify if bed bugs are present. On the other hand, bites that occur at various times of the day in various locations such as at home, in the car, at work, etc. are much less likely to be caused by bed bugs. It is also important to realize that just because you have looked for bed bugs and could not find them, does not mean that they are not there. These insects lead a very cryptic and secretive lifestyle and will often go undetected. It is best to have a highly trained professional conduct the inspection for you.
Occasionally you may see evidence of a bed bug infestation without actually seeing any bed bugs. Bed bugs leave fecal stains in the areas they inhabit. These stains are actually partially digested blood but remember that it will not be red unless you crush a bed bug that has just recently fed. As the blood is digested it turns black and therefore the bed bug droppings usually consist of several black spots in one area. The fecal spots will not flake off if rubbed and will smear if wiped with a wet rag.