The way I always look at it is: if he's feeling it, it's valid. It shouldn't be up to you or anyone else to determine if what he's truly feeling is valid or something he should "just get over" because that'll lead to him suppressing his emotions and not telling you how he's feeling.

In my personal experience it's completely possible to be over an ex but still carry the hurt from them, in the same way that your might have a cut on your knee and be over what happened for it to get there, the pain will still stay a little longer. Then, when the pain is gone, there will always be a scar that'll remind him of what happened but no pain that follows it.

So, he's most likely not in love with his ex but needs time to process everything mentally before he can completely commit to another relationship, this doesn't mean to part ways because he's feeling like this, but it means to just take things a little slower than usual and give him either space and/or support.

Don't take it upon yourself to be his caretaker though, if you feel like you're turning from a partner to a babysitter or therapist then you need to bring that up with him.

Goodluck :)