Long distance relationship advice please!

So my boyfriend and i have been together for almost 5 years and only a year of that was spent together in the same country. He lives in Australia and I live in the Philippines.
Lately hes been going out with his colleague (girl of course) and he even takes her home. Hes been doing this rather often now. Work together, dinner then takes her home. Of course im super bothered about this because this girl gets to spend so much time with him meanwhile i only get to see his face on a screen. He was never like that with me when we were just bestfriends. He never took me home. So weve been fighting about this. He doesnt get why im so depressed about it. Should i be worried and am i being difficult? Please help..