Sorry to be nosy but can I ask why you don't live together after 2 years? That's a pretty significant amount of time yet from what you're saying he's treating you like you're still in a new relationship. [Edit to add - I've just seen your posts mentioning your children from a previous relationship and living 1.5 hours apart - so maybe it's time to ask yourself where this relationship is going? This doesn't seem very sustainable long term, IMHO.]
I don't care whether you're 6 or 60 - a birthday is a birthday and if you want to make a fuss to celebrate it, you absolutely should.
Having said that, this isn't the end of the world. I'm sure you can have a weekend away whenever and it sounds like this conference might be a one-time thing which is important for his career and/or networking. You can't hold him back from that otherwise it's just going to breed resentment. Unfortunately this is life and long-term relationships require some compromises (no excuse for him calling you crazy, though!). Let him go, reschedule the trip, and see if he tries to make it up to you. If it starts becoming a regular pattern of behaviour, then you'll know you have to move on.