Interesting, because in my culture, therapists don't tend to ask patients about romantic relationships and sex. It's actually rare to have a therapist willing to be open to the topic.

Took me years to even ask my T if it was an OK topic, and I was relieved when she said of course its OK and that no topic that's taboo.

I think perhaps your T is waiting for you to broach the topic, although it can definitely help if he preemptively signaled openness like "I'm willing to talk about the topic and I'll wait for you to bring it up."