Christina Haack and Josh Hall‘s breakup wasn’t just a surprise to fans … we’ve learned the realtor was also blindsided by his new single status.

Sources close to Josh tell TMZ … he knew there were ups and downs in their marriage, but never expected his relationship with Christina would end this way. We’re told Josh was seriously committed to Christina … as his social, professional and romantic lives all revolved around her.

Josh was also dedicated to Christina’s kids — Taylor, Brayden and Hudson — from prior relationships.

According to sources, Josh feels like he’s lost his whole world, especially because he dearly loved Christina and their life together. Josh felt they grew together as a couple … as they had been able to buy their dream home in Newport Beach and undertake various TV projects.

Bottom line … we’re told he’s very sad Christina chose to end their marriage.

Our sources say she stopped speaking to him after a disagreement and would only speak to him through an attorney. Josh also hired counsel once he realized where the marriage was heading.

We’re told he’s spending time in Nashville these days, where he’s been hitting the gym and regularly attending church — and despite the marital shock, he’s feeling optimistic and wishes nothing but the best for Christina and her kids.

As TMZ previously reported … Christina and Josh made their split known when he filed for divorce earlier in July. Josh cited “irreconcilable differences” as the reason for their breakup, noting their separation date as July 8.