Three Knocks On The Left Side Of My Head While

Three knocks on the left side of my head while I am just falling asleep during sleep or just waking up. Was on prescription benadryl taken 3 a day and as of last Tuesday I haven't taken any and I still have the knocking. Today while I was napping there appears to be a new sound which I haven't been able to figure out what it was. Now I would of swore the knocking was actually on my walls and not aware it was in my head till last week this as been going on for approximately 2 months.