I think this situation would have worried any woman. Not so much the flirting (which was enough) but then a message too. At some point you have to let it go though. I guess the situation is made better or worse by how much you trust your partner. The fact that you don't get along well probably is causing the obsessing. It also feeds into whatever insecurities that you have. The insecurities can breed this doubt which is why you can't let go. Men buying you drinks won't help. It may make you feel sexier but it won't do anything to help you let this go. I can see how that would make you feel desirable though. It makes you feel like you are still attractive. But when you get home you will still be thinking about this. Because you will still feel insecure about the relationship. Instead talk to him at length to see if you can find comfort in feeling secure and better about the relationship
Don't worry about how you sound. If you have a good relationship just be honest. It's okay to feel insecure once in a while. You can feel that the relationship needs rekindling. This is a chance to address that. I would bring up both and communicate about all of this. This seems to be what you need so do it. You deserve to get all of this out and to work it out as a couple. Begin to build on your relationship. Institute date nights. Find quality time just for the two of you. You will end up feeling that this stimulated a healthy discussion.
Going to bed now but good luck. Discuss this with your partner.