Sharing Our Innermost Thoughts

Recently I was seeing my BF instagram ID and i really dont know why but i started to feel jeleous by some of the girls in the group photograph. Its is completly normal for him having other female friends except me but i really dont why but i have that inner insecured feelings.
I also have male friends and he also have female friends ,then i really dont know why there is such inner gut feeling which is telling me that he might be in more touch (attracted) with them then me. I have travelled few months to my family back to take care of my parents and its been a while since i have came back and he is still there. We barely text and video-chat or even call. Most of the time he is busy studying (so he says) and i really dont know how to get past this stage…
If i tell him this then he will say that there is nothing to worry about and everythings is fine and all that talks (trust me; i wont do anything like that behind ur back etc.) maybe not even knowing if he means it or not ,or just saying for saying sake. And if i dont then this thing will eat me from inside. This long distance relationship will drive me nuts. What should i do in this circumstance??