Sharing Our Innermost Thoughts

I recently started dating my best friend of 5 years since 6 months. It never bothered me before that she used to go out with her friends always and have fun… And even i never cared much back then. And i know how much of a great person she is. But we started dating on the same thing taht it won’t be a much of an hassle. But my previous relationship wasn’t great and i had serious insecurities. And now after we started dating,i have started being extremely jealous of her, i feel very very jealous when she goes out with her male friends and also when she goes out late nights and all… I really don’t know why. I know what she is. I really trust her. But i don’t know why I’m so freaking jealous and irritated that she’s having fun with someone else. I feel like I’m ruining it coz of all the jealousy in my head. What should I do. I can’t talk to her. She’s too sensitive and she’ll take it very seriously. I really need to work on myself. But i don’t know how. I feel like i should be happy if she’s happy and empathize her and make her feel better. But I’m really not able to. Whenever she brings up anything regarding her friends, i suddenly become low and get strange which she can easily notice and i can’t help myself but to act out that way. And i always defend but to be honest it is actually bothering me. I’m really scared to lose this but also i don’t why I’m so jealous and insecure. What should I do. What am i doing… Is this because my previous relationship scarred my emotions so bad and am I still the same person and still acting out the same as i used to. Idk what to do…