You can carry a tune and follow a melody. That is great, I don't know if that can be taught. Feel the strain in your throat? The tightness at the "bottom" of your throat? That's mechanics. All of our vocal mechanics for speaking are wrong for singing. But, that is all we know, so we try to push through it. For example in speaking, we tend to effort on the inhale and just let the exhale happen. Singing requires the opposite. Effort on the exhale (push up from the diaphragm) and inhale becomes effortless. We tend to pinch notes out of our throat, instead of letting them fly out of mouth. Push air up, from your diaphragm, through a relaxed throat, and you will find the notes flutter from your throat, instead of being squeezed out of it. Imagine you are directing a geyser of air from the bottom of you stomach, up through your chest and throat and straight out of your mouth. That's the basics, as I understand them. Then you will learn to control your throat and bounce the air around in your head, and magic will happen. You local voice coach is invaluable in helping you with the foundational mechanics. I'm not one, but I do appreciate them.