Start with what
you actually know.
When someone feels distant, the mind is quick to fill in the gaps. “He was quiet at dinner” becomes “He doesn't want to be here.” The first sentence describes something you noticed. The second is one explanation. It might feel convincing, but it is still an explanation.
Clarity begins by making enough room to tell those things apart. You are not being asked to dismiss your feelings or find an excuse for behavior that hurts. You are giving yourself a more reliable starting point.
A small exercise
Choose one recent moment. On a piece of paper, make three columns: what happened, what I made it mean, and what I need to ask or observe.
What happened: We ate dinner while he looked at his phone.
What I made it mean: Spending time with me doesn't matter to him.
What I can ask: Could we have dinner without our phones tomorrow?
This example is fictional. Your situation may be different. Notice that the request is specific and possible to answer. It does not require your partner to prove a feeling on demand.
Pay attention to the next part
A reassuring answer matters less if the pattern never changes. A single awkward conversation also cannot tell you everything about a relationship. Over time, look for willingness, follow-through and respect for your needs. You can be kind while taking those observations seriously.
If a reasonable request brings intimidation or makes you fear for your safety, couple exercises may not be an appropriate next step. Seek individual support and put safety first.