A good liver

Around 15 (fifteen) days ago, I noticed there was a little/some water inside my left ear canal. I noticed that because I turned my head suddenly and I felt liquid moving inside my (left) ear. As I swim frequently, I am used to having water inside my ears canal because I am a swimmer/ I swim frequently and I know that all I need is to bend my head to the side ear affected site and press the ear entry with my finger in order to take the water out (of my canal). Even though I sometimes have to repeat that process, it always works. some times, I always can solve it. Today, however, my method is not working now. Today at This morning, my mother, who is a doctor, examined my ear and realized that the water is actually behind the eardrum and she gave me some medicine to take.
Up until three weeks ago, I was not noticing that I had I had never noticed my ear canals [,but now I am very aware of them because the water inside is really annoying]. Now, as water inside it is really annoying me, I remember that part of my body many times by day . As a professor of mine says: "a good liver is that one you do not know that exists". The same can be said about ear canals.Thank God I am never as aware of my liver/ my liver is not always reminding me of its existence  keep not remembering my liver.

---

A good liver

Around 15 days ago, I noticed there was a little water inside my left ear canal. I noticed that because I turned my head suddenly and I felt liquid moving inside my left ear. As I swim frequently, I am used to having water inside my ear canal and I know I need to bend my head to the ear affected site the side of the affected ear and press the ear entry ("opening" perhaps?) with my finger in order to take the water out of my canal (This is correct, but it seems redundant.  It could be omited from the sentence and we will understand.  Also, I don't think any native speaker would say "canal" without saying "ear canal".).  Even if I have to repeat that process some ("a few") times, I can always can solve it. However, my methods are not working now. Today at This morning, my mother, who is a doctor, examined my ear and realise that the water is actually behind the eardrum and she gave me a medicine to take.
Three weeks ago, I was not noticing that didn't notice I had ear canals. Now, with water inside it is really annoying me, and I remember that part of my body many times by a day. As a professor of mine says, "a good liver is that one you do not know that exist". The same can be said about ear canals. Thanks God I keep not remembering my liver. (The phrasing in the last sentence is unusual, but even so it's something I might have said myself.  Sometimes native speakers do phrase things in an unusual way.)

A good liver

Around 15 days ago, I noticed there was a [little]/[bit of]/[some] water inside my left ear canal. I noticed that because I turned my head and suddenly* I felt liquid moving inside my left ear. As I swim frequently, I am used to having water inside my ear canals and I know I need bend my head to the ear affected site and press the ear entry with my finger in order to take the water out of my canal. Sometimes, I even have to repeat that process (a few times), I can always solve it. However, my methods are not working now. Today in the at morning, my mother, who is a doctor, examined my ear and realised (/found out) that water is actually behind the eardrum, so she gave me a medicine to take.
Three weeks ago, I didn't know was not noticing that I had ear canals. Now, as water is inside it is really annoying me (/it really annoys me). I'm reminded of (remember sounds a little bit weird to me in this case) this body part many times a/per by day. As a professor of mine once said: "a good liver is that one you do not know that exists". The same can be said about ear canals. Thanks God I don't keep not remembering (/I'm not constantly reminded of) my liver.

* Did you turn your head suddenly or did you feel the water suddenly? To me the latter sounds more logical. But it's matter of your preference of course.

If there are any unclarities, just ask! ;)

My English isn't flawless, so this correction may contain some mistakes. I was a little in doubt on what to do with: ''I remember that part of my body many times''

Anyway, I think you wrote well! I hope that pesky water leaves your ear canals soon so you'll forget you have them! ;)