Am I right to be suspicious? Or am I just being Paranoid?

I think she is turning to other guys as well but I think part of the reason may be because you are too protective of her. For example keeping an eye on the clock for when she will be back from the movies and questioning her all the time *just read the end of your story so far and yes it is creepy*. That would make her run for the hills. If she wasn't cheating before all that she'd want to after that. Everyone needs some freedom and if you want them locked up with you and get paranoid about every little thing you're not going to last. I know because my boyfriend is like you :P. Thing is it makes me want out when I feel like he's watching every move. If I am having a conversation with one of his male friends or any other male he always comes in to cut the conversation short and take me away and he doesn't even like me spending time with any of my female friends because it takes away time I could be spending with him - he wants it to be just us 24/7. Anyway I've spoken to him about it and it's getting better but you need to take a chill pill and back off a bit. She deserves to have a life as well without you prying into everything she does.