I think you are very angry mate which is fair enough and i sympathise for your situation, but i do feel the anger is making you jump to conclusions with this affair thing. Please dont take this the wrong way as no offence is meant but if your wife has a young child, a job and possibly some housework responsibilities how on earth would she have time for an affair or even have the energy?! I know i dont know anything about the job she may have or whether you fully take care of the child and do the cooking etc so please dont be offended by this but i really agree with supertech, that you should get some counselling before you jump to conclusions.
Unconciously because you think your wife may be having an affair you will behave negativley around her which will only make things worse, and your son may pick up on this negativity (children, even young babies are very receptive of this)
It could be your wife is having self-esteem or confidence problems since the birth of your son, or even post-natal depression which has not been diagnosed. Sit her down calmly and have a nice chat with her. Having babies can do strange things to women!
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