It sounds as though you may just have been a bit too laid-back about the whole thing, because it takes us guys a lot to show that we like you. So, when we've instigated flirting, stepped out of our comfort zone, asked for your number and put in the effort to not be an a$$hole around you, we often end-up wandering why we did it all because you've not really 'stepped it up'. It leaves us wandering a) If you really do like us, b) Whether there is any more to you that not everyone sees and c) How far are we going to have to go to really break through?
I know you say you're not boring and I'm not saying that's the problem. I'm just saying that it requires something a little bit extra special to properly connect. Try pushing a little harder to be a bit more intimate/close/fun at certain moments (not to be mistaken for clingy-ness).
Sorry if this is a little bit non-explicit but I think most people know how to make things a little more special when they really want to. x