Hello! I am taking Diphenhydramine as means to help me sleep. For five years it has helped my insomnia decrease in it s levels. I usually take anywhere from 75-125mg every night. The dosage varies depending on how much food I have eaten beforehand. Lately, as in the past 7 months, I have experienced a strange side effect, or so I think. It feels like my pulse is very soft. Normally I can feel it beating, but after ~30min of taking Diphenhydramine it becomes very quiet. I press my middle finger very hard into my neck to count my pulse. It s ~84, and my natural HB is 75-85. As I keep my middle finger there, though, it feels as if my heart skips a beat or three, and then beats extra afterwards. Every time I think it is happening, I become very anxious. The medicine makes me feel very drowsy, so perhaps I just zone out and think my heart skipped a beat. I honestly do not know. However, once I became very anxious due to the medicine s possible side effect. I was sitting on my bed, and I couldn t feel my pulse. I got up and ran into the other room while my eye vision blackened, but a few seconds later I was completely fine. Strangely enough, at least to me, is I can breathe just fine when this happens. My breath does feel a little delayed, though. I stop inhaling with my mouth, but my lungs don t stop expanding until ~2-3sec after. It almost feels like my lungs are working through mud when I breathe. In short, I can only feel my heart beat when my fingers are shoved upwards into my neck. However my pulse seems fine when I count it. It feels like it flutters every now and then.This only happens after I take Benadryl. It s a little difficult to breathe, that may be due to my asthma, but it feels intensified when the medicine is at work. What do you think? Is Benadryl giving me heart palpitations? Or am I just paranoid and zoning out too much to realize my normal heartbeat? Should I stop taking it altogether and get a prescription for a sleeping aid? Thank you so much for you time, and I hope you have a wonderful day!