Am I Being Paranoid? Girls opinion

well when me and girlfriend first met everything was good she was very happy and we were living the life but all of a sudden she started gaining weight and now she is trying all these diet plans to lose it she is a bigger girl so I didn't get to paranoid but my friends started telling me that this is what girls do when they are cheating start caring about appearance a lot and its got me a bit paranoid she told me "she is trying to fit back into her clothes and I want you to support me" I have had suspicion of her cheating b4 but I have been cheated on in the past so maybe its paranoia I don't know what to do I need help am I taking this to far?
Am I Being Paranoid? Girls opinion
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