Its normal. When I first started
vaping i went straight to 36mg and I hated it so much because it would destroy my throat and make me cough. For the first week or so, as soon as id inhale, my lung would collapse and force the vapor back out making me cough in the process. That is long gone now unless I take a big one first thing in the morning.
I dropped down to 18-21 mg on a regular 3.7 e-cig which was okay but a little bit too strong. To me the sweet spot right now is 12mg
juice on a 5v e-cig. That setup reminds me of an actual cigarette (inhaling thick air instead of small pieces of glass/sandpaper). However I know it is still much harsher than a true cigarette because when I have one, it feel like air and I get no throat hit at all. On top of that, when a smoker friend tries my e-cig they cough real bad and complain about how harsh it is.
Whatever strength you are
vaping now, id suggest cutting it by half give or take and try it. You will most likely get no throat hit at all due to the sudden decrease in nicotine, but after a while you will notice that there is a throat hit.. and a pleasant one at that.
Good luck and dont give up.