Its too bad you don't want to talk to her Tiny. She could offer you some much needed insist to what has been going on for him and likely clear up a few of the things you have been imagining. You might have a few laughs about how he is and end up getting each others back some time if he finds a new "toy" (used playfully here). She is likely curious and wants to solve a few of her own mysteries about him. Just as you do... you are both dating him no? Likely she is experiencing the same stuff. He might just be telling her that he wants a relationship with her too.
Most of the drama, anxiety and stress you caused yourself here seems to be BECAUSE of the DADT policy you have. DADT actually causes less trust, less connection and keeps relationships at the surface. He will never have the good fortune of a really deep and connected relationship with you if he is forced to hide a big part of his life. You have enabled him to have a life away from you and that means you will not get the full him. She and other women are just as likely to make up who he is as you are. Why would you not want to know about that?
If you are just an option for him and you don't mind that then great, if you are a priority to him then I think it would serve you both better to drop the DADT and do the hard work to make this a solid relationship. You already have a shaky foundation, why add to it with putting blinders on about what goes on in your lives just for the sake of becoming overly emotional and needing to do some work together?
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