Yes, don't try to be any one way or another because if you are not yourself, then it won't work anyway. Jealousy is natural. We all feel it from time to time. It is an emotion like any other. We have to learn how to handle it. One way would be to not read his texts and let him be in that regard. He will have female friends and girls who like him that will text and that is just the life of a teenager guy. You probably have some male friends and boys who like you too. So, just don't put yourself in a situation of getting overly involved in what he receives in the way of texts, phone calls or attention. Tell him that if he wants to be with you great and if he does not, to let you know before he goes out with anyone else. That you trust him in that regard to do the right thing and to either be with you or set you free. This is the mature way to handle jealousy and other girls.
When we try to control it, we get into trouble. YOu are both really young and have a lot of years ahead of you---------- so just think in terms of enjoying what you have and seeing what happens in the future.
Good luck. I know it is hard but do not let jealousy get the better of you. Keep it as any other emotion to deal with and handle without too much disruption in your life or relationships.
the mixed signals in this relationship is probably what is causing alot of the upset,just tell him honestly how you feel this way at least you will know where you stand,you are young and should be enjoying yourself not worrying if you are cool enough for him or not in your case,good luck