Every member of your local Board of Realtors should have access to the Multiple Listing Service, where every home that is for sale where a licensed realtor is listing the home will be available online. They can pull the "listing" and it should indicate when that particular listing was started, and more importantly, it should list how long the property has been on the market in total. The latter, "in total", refers to the situation where a home might have been listed multiple times, possibly by several different agencies. What you want to know is not just how long the current listing has been active, but how long in total, the property has been listed for sale by anyone, in the recent past.
Many Boards of Reatlors have a guideline similar to the following: ADOM - meaning Active Days on the Market, is the acronym for how long the current listing has been active; CDOM - meaning Cumulative Days on the Market, is the acronym for how long in the recent past the home has been offer for sale.
CDOM is the number you're typically most concerned about. For example, here in Austin, Texas, we will continue to add days to CDOM as long as there has not been a gap of more than 90 days from one listing to the next on a given property. Let's say you just get an answer that ADOM is equal to 30. That might cause you to conclude that the house has only been on the market for 30 days. Not bad in most markets. But, if for example, you found out that CDOM was 170, that means that in one form or another, the house has been offered for sale for almost 6 months.
And as said before, I'd recommend getting an agent to represent you so that these types of questions get answered by someone who has your interest at heart.