Is it ok if my bf overprotective of me

Well my bf is acting paranoid and every time I take like 5 min to text back he text me and say who are you texting is it another guy he said that he will be mad if it is but it was actually my friend girl and not to mention this morning he told me that I was going to leave him if I found another guy he just started acting like this morning and he told me I was his territory and I really don't know what to do I'm only 18 please give me some advice or your opinions everyone