I have a "heartbeat-like" pounding in my ear, but I don't think it's Pulsatile Tinnitus. Any ideas?

It’s been happening on-and-off for as long as I can remember, years and years. Recently it’s gotten a lot worse, with frequent occurrences (usually 8-10 hours long) each week. It’s not always constant – it can also go on for several minutes, stop for a minute, then continue. Often when this is happening, any noises at all around me (even the sound of my typing or people talking at normal volume in the next room over) will cause a sympathetic “boom” in my ear (I don’t know how else to describe it…it’s the same sound as the heartbeat, but in time to outside noises instead of my pulse). It most commonly happens in my left ear alone, but occasionally in both ears at once. I’ve also recently noticed a hearing issue – I can hear fine, both very high and very low sounds, but I have trouble differentiating between sounds (any background noise at all can cause me miss what people say). I am not stressed at all. I have perfect blood pressure, perfect cholesterol… I’m 22 yrs old, and female.
I do clean my ears of wax regularly, using the warm water flushing method, and I’m sure it’s not a build-up of that.

This sounds like a neurological hearing problem, we see this frequently in the clinic, people can hear sound at normal levels, but have difficulty understanding speech, it’s called a central heaing loss. And as far as the pounding, it IS tinnitus, if not that, then your ears are so sensitive that your hearing your own otoacoustic emissions – the sounds that come out of your ears. Hope this helps, good luck!