Raquel: Your Realtor can show you any and ALL the comps (Comparables,) including: available on the market, (competition,) Pending closing and recent sales that apply to your area. At that point, you will know as much as they do about what your place is worth today, except that they may have visited a few of them in the course of business and give you some further insight into condition.
At that point, (again) you will have to make up your mind as to what you wish to do. That will take into account why you want or need to move.
Before you decide that now is not the time to sell, remember that, just as your house is worth less now, so would most replacement homes. A fair trade off may get you better housing for your purposes. The mortgage rates are very good now and will help you by allowing your investment to grow more rapidly, something that may not happen in the future. The future is the great unknown. Even economists disagree and have wildly different forecast of how things will play out.
You can put your house on the market for any price you choose. The agent who told you that she could not put your home on the market was speaking of her own criteria. Other Realtors might put the house on the market for far more than that and hope that either you would lower it later or the market would recover. There is neither law nor custom that restricts what price you can place on your own property. If you go too far overboard, you may not find an agent willing to waste their time. This agent, presumably, has decided that anything beyond $275K is a waste for her. Good for her but perhaps even better for another agent who is more flexible.
Lots of luck