How Can I tell if my girlfriend is cheating on me?

Is it just the reason. who knows she may truly be having litys of work? why suspect her if she goes to office early? If you have doubt, have a clear chat.

There is usually a laudry list of things such as you described that could in fact indicate that she is cheating on you. But let me tell you one thing, and that is if you do not trust her now. You never will and what is a relationship without trust?

Well honestly this is not a sign of cheating this could be a sign of her just tired from work. If you want to catch a women cheating you have to pay close attention to details because women are going at cover tracks ok! I found the perfect article from askmen.com that will help you determine whether or not she cheating. http://www.askmen.com/dating/dating_top_ten_60/65_dating_list.html

Well , no idea how can u find this at all, maybe try a movie tricks? Get an agent who will look for her and what she is doing,although if she does find it out, and never cheated on u, probably your relationships will be damaged.. or stoped at all... consider this all, maybe its just better to wait or ask her, where she was? O_o