Insecurities and Doubts in My Relationship

**SORRY, LONG RANT** I'm on an emotional rollercoaster with my boyfriend.I understand he is busy at work but he used to text me in the morning and during the day. We both use an app that shows when we're on line and I pop in and text him a little note when it shows he's online and then he doesn't respond and disappears( yes, I do wait for a response from him about 15 minutes).He doesn't use this app for work only to text me. I'm a very insecure woman and he knows that I am and reassures me that I'm his "babe"...lol I did ask him who he's texting with and he got offended right away. I thought that was odd and out of character for him.Then the next day he tells me he loves me and wants to be me. I think, in my opinion, he's talking to another woman but that's my doubt and insecurities clouding my logic and the way I feel. Please, I need advice and be kind to your advice and comment.🙏Thank you🤔