Nobel laureate economist Robert Shiller isn't quite sure what to make of the housing market at this point.

"Our indices [the S&P/Case-Shiller home price indices] are basically flat right now," he told ETF.com.

"It’s seasonal weakness. If you correct for seasonality, it looks like they [home prices] are still going up. But other indicators are showing signs of weakness, so I’m conflicted."

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The S&P/Case-Shiller index for 20 cities showed that home prices rose a seasonally-adjusted 0.8 percent in February, while unadjusted prices were unchanged.

Meanwhile, both new and existing home sales fell in March.

"In the past, I’ve learned that home prices show a lot of momentum, and the fact that they [prices] are flat doesn’t necessarily mean there isn’t still momentum," Shiller said. "But there are other indicators that point to weakness in housing."

In addition, the government may pull its support for mortgage agencies Fannie Mae and Freddie Mac, he said. And it's unclear how much home-buying major investors like Blackstone will continue to do, Shiller said.

"There are many reasons to be worried right now, even though the market at this point still looks like it’s going up."

Other experts too have their doubts about the housing market's strength. "The days of very robust home-price gains are over," Thomas Costerg, a New York-based economist at Standard Chartered, told Bloomberg.

"Elevated price gains are a headwind, especially for first-time buyers. Prices will slow going forward, and the housing market needs that to recalibrate supply and demand."

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• The Guardian's Moore: Housing Market Still Isn't Recovering