Thank you for your question and I'm very sorry to hear about your situation at work. I'm bound by my legal duty to tell you the correct answer about your situation above, and sometimes that is hard when the answer is that you most likely do not have any legal recourse.
Harassment at work is only illegal when the harassment is based on discrimination
regarding age, disability, race, national origin, religion and/or gender. The law allows for your co-workers to be mean and hostile
to you (as long as they do not assault you). So, unless you can show that the harassment is based on illegal discrimination, it is not illegal.
The other problem is that you said you cannot prove anything and that you have never heard anything directly said to you. If you find out that a person is spreading untrue statements of fact about you which tend to hurt your reputation, then you can sue that person directly for defamation. However, you need to know exactly what they said and who they said it to, otherwise, you would be unable to prove your case.
I know that hearing this is not encouraging (unless you fit into one of the categories above). Please don't "shoot the messenger" and consider kindly rating my answer positively. Please also feel free to ask any questions you may have.