My Boyfriend is Jealous of My Best Male Friend at Work

He is about to ruin my life, Laila. 

 Hello everyone, 

I have been in a relationship with my boyfriend (he's 32) for around 5 months now. We love each other very much and up until now, we haven't had serious issues to quarrel or worry about. 

Last week, my bf started asking me questions about a certain guy friend at my work place named CJ. 

I was surprised because CJ is my boss at work. Or rather, here's a little detail about me and CJ - we are coworkers though not even in the same branch, he works at our Head Office and once in a while, visits my branch to relieve my immediate boss. I won't lie to you guys - CJ likes me, I like him too and we had always been really good friends long before my current boyfriend walked into my life. CJ is even currently in a relationship with another girl and I have always been genuinely happy for him. 

I agree that we do communicate through BBM and whatsapp regularly and once in a while it does get intensely flirty between us. CJ says he can't resist me but ever since I met my man 5 months ago, I toned down on the flirting and started acting more friendly instead.  

CJ has never visited me at home or ever met my boyfriend before, so you can imagine my shock when out of the blues, my boyfriend now started asking me about him. He started acting odd and has now developed a bad habit of impromptly calling me while I'm at work and asking me where I am, who I'm chatting with on my office computer and all what not.  

One time, it happened that CJ was around my office after work and asked my girlfriend and I to join him for a quick after work bite at a restaurant. My boyfriend called and when I told him the truth that I was hanging out with CJ and a friend, I would never lie about that, he went ballistic. He started saying a lot of things that showed he knows a lot more about CJ than I told him. Obvious signs that he's been definitely looking through my phone or he has outside sources. 

I've assured my boyfriend COUNTLESS TIMES that I see CJ only as a platonic friend but I don't think his body language and his actions are trusting me. 

The one that is driving me mad now is that there's a 5 day conference my office has organised. CJ is attending, I am to attend along with a few colleagues. You won't believe that my honourable boyfriend has sworn I won't attend it. My job is on the line, we are to leave this Sunday for the Abuja conference and my boyfriend is adamant that it's either him or the conference. I was packing up for the conference when he visited my house yesterday. He saw my packed bags and the way he flung my stuffs away got me pissed off and we ended up in a big fight. He wouldn't exactly say it's because of CJ he's not letting me go, instead he is saying that he's no longer comfortable in our relationship and that I need to pick one. 

What do you think I should do, please?