Boyfriend likes another girl?

My partner and I have been together 8 months now. We live together and are so perfect for each other.

Recently he started a new job at a bank and for the last couple weeks I'd heard him mention a girl's name quite a bit. Because I'm a no bullshitter I asked him straight out " do you like jess more than a friend". His response was "I don't know. I'm not good at understanding my emotions and need to process it more".

Those 24 hours were hard. Thinking what he was going to say. He eventually messaged back and said "you're the only one I want. I love you. I find her attractive but not sexually, it's hard to explain. We are just friends".

I went to meet her last night at his friends work drinks. She's not what I expected. Quite opposite to me. Which makes me feel insecure.

My concern is that he couldn't say no straight off the bat, he had to think about the answer. This scares me, it makes me feel insecure in this relationship. Where is it headed?

I need help and someone to chat to. This is wracking my brain. I'm usually not the jealous type so this is breaking me.