I've never heard of bipolar without cycling. If you don't ever become manic but just get depressed and have mood lability I think just BPD and depression make sense.

I sometimes can't tell when I'm having an episode. I get upset when someone tells me I am in an episode when i don't feel like I am and I stay in denial until it gets pretty bad and then I believe it. That doesn't sound like what you're going through though. It sounds like you're having trouble distinguishing what emotion you're having at any given moment. I don't feel like I have that problem.