Your loss might be in a specific Hz range. This could explain your not understanding or hearing sometimes. I'm sure an audiologist can help identify this range and should be able to provide you with a chart that helps you to understand what speech sounds you are missing. You might even ask the audiologist to do a more comprehensive testing of more frequencies to get a better picture of your hearing. I will have to check my audio testing equipment to see if this is even possible.
A lot of hearing folks are surprised to find out that they do have a measurable loss and never knew it.
As I've been realizing that the things I'm experiencing are symptoms of hearing loss, I've been seriously surprised and shocked. I figured I had some sort of undefinable audio processing problem or something. I didn't think about it too much, really. Now that I'm paying attention to my issues, I'm really stunned at how much more extensive my problems are than I previously thought.
It varies depending on background noise conditions and the person I'm talking to, but based on my observations, my comprehension rate for phones can drop to as low as 40%. Even in good conditions, I'm usually closer to 80-90% comprehension than 100%. This is also true in other situations, such as noisy offices, long monologues, television shows, etc. Hell, if I'm talking to someone and a simple sound like a passing car or rustling bag or gust of wind comes past, I lose comprehension. It doesn't even have to be all that loud.
It makes for embarrassing work meetings sometimes where I'll mishear things and respond to the wrong thing, causing people to all look at me funny because what I said has nothing to do with what was actually being talked about.