My wife is suspicious of me for no reason. Help!

I am married since 2003. Soon after marriage my wife always suspicious of me having affair with someone. First she doubt on her own sister. Then she started doubting my female students. I have to stop my coaching centre and leave the city as well. Started job. Where ever I work definitely there was some female colleague and my wife suspicious about them. It create lots of problem for me. I have seat with her several times to make her understand that this job is our bread and butter. I was always open to her, tells everything about what happend each day. For last few years she behaving extremely odd, using slangs (which I never used). I have talked to her parents also, but they are also not co-operating. Our child is growing up. She insulted me just before my son. Please help.