He clearly did do something wrong, as the OP told him before she had sex that she wanted an exclusive relationship and she was u see the impression he agreed with her... until after when it transpired he said that simply to have sex.
So yes, the OP needs to work on her boundaries. But I don’t think throwing all the blame for this on her is at all helpful. Excusing his behaviour just because it’s typical mans ‘get sex no matter what’ behaviour is not ok.
So please don’t take on all this new blame as more relationship baggage OP.
Yes, there are clearly things you need to do differently in order to keep your heart safe next time, and also be a bit less full on and vulnerable. But don’t think this is because you were to blame for the actions of a slimeball (oh sorry, I meant bohemian), taking advantage this time.
Before you date again, I’d really take a hard look at your boundaries, and be careful and slow about sharing things that let you become vulnerable next time. Another poster puts it really well, sharing personal things very quickly creates a sense of false intimacy. That’s the last thing you need, as you are trying to negotiate your way through the tricky ways of online dating, whilst being a little vulnerable yourself.
I also think that unburdening yourself of all this highly personal vulnerable stuff doesn’t have the effect you want it too, or the effect I’d want it too either, so your thread has given me food for thought for when I eventually feel ready to date again! I naively thought it might make people behave slightly more honourably, or gently at least, but thinking about it, of course it’s just showing how easily you can be manipulated.
And if you are sharing all this too early on of course, you may put off a nice person because it feels a bit ‘off’ in rhythm to be sharing such personal stuff too early on before the right bond has been built.
Have a look for the ‘sharks cage’ metaphor of boundaries, it’s really relevant to your situation.
As I recall it was a psychologist in Australia that came up with this idea, after seeing so many women with gaps in their boundaries routinely letting in ‘sharks’ because their usual boundaries and armour just arent equipped to keep out the predators and invite in all the other wonderful sea life that exists when predators aren’t around...