Dates go well, sex happens, then they lose interest after a few dates. What am I missing?

So, lately I (28M) have met multiple pretty women, either through dating apps or in real life.

I know I'm not particularly attractive, but I have a good career, I'm independent, I've had relationships in the past, and I think I'm a decent conversationalist.

Quite often the dates go well and many of them lead to sex on the first or second date. Then we usually see each other a few more times, but after 3–4 dates they gradually stop responding to my messages or reacting to my invites.

I'm looking for a relationship if I feel there's mutual romantic interest. Otherwise I'm perfectly happy keeping things casual. The problem is that they rarely seem interested in continuing either way.

I don't lie to them. If they ask whether I'm seeing other women, I'm honest about it. Sometimes I wonder if that's a mistake. I also wonder whether I'm perceived more as the "smart" or "safe" choice than the exciting one, and whether admitting that I'm dating other women makes me seem less reliable and undermines that image.

A few years ago I had serious relationships. Nowadays my life is objectively in a better place, I have a stable job, I'm financially independent, and I have an active social life, but as I've started dating women I'm more physically attracted to, the outcome has become almost the opposite: things start well, but they almost never last.

I'm genuinely wondering whether there's something I can improve that's within my control, or whether this is simply a normal part of modern dating that I need to accept.

Another possibility I've considered is that maybe I'm simply not very good in bed. The thing is, I honestly have no idea how to judge that. None of the women I've dated have ever complained or given negative feedback, but it's not exactly something people are usually honest about. Since I have no way to compare myself to the other men they've dated, I don't know whether this could realistically explain the pattern I'm seeing. Also I don't know how to improve this, this was not a problem in my past relationships.