I've been experiencing somewhat similar thoughts about my job. I've been convinced my co-workers are sick of me working there and are conspiring to get me fired. I listen to every conversation they have together if I'm within earshot and assume parts of the conversation are about me. Then I interpret every little event and coincidence as meaningful.

Your stress level might be contributing to your paranoid thoughts. Is there any actual evidence people at work don't like you or think you work too little? To me it sounds like you feel pressured to take on the extra work but you do not necessarily have to be doing it. The pressure seems to stem from the paranoia. If you continue with this vicious cycle I fear you might develop worse symptoms.