All of the answers below are good ones, but one thing that was left out is the condition of the home. Your agent should have gone over staging with you, and it's extremely important to follow his/her advice in that area. Things such as uncluttered rooms, maintained yard, clean home, etc... go a long way towards presenting the property.
If you do decide to make a switch, make sure to end your listing agreement with your agent before interviewing new ones. I don't mind lending advice on the topic, but I would think any agent here would have a problem actually trying to earn your services while you are working with another agent for ethical reasons. Once you are free, make sure you interview 3 or 4 agents to decide on your next real estate consultant. Consider all of the advice given here, decide for yourself why it hasn't sold and then make sure the next person you hire can fix that problem.