Is it normal when i lay down to sleep i feel every pulses in my body pounding?

Hello, I'm 22 years old. I smoke and drink. I'm kinda overweight but not too overweight. I seldom eat vegetables. I'm also a very anxious person.

So my problem is, I was living in my apartment for like 2-3 years now and there comes this time (two months ago) when I'm going to sleep lying down in my bed I feel like my heart is pounding to much. Every time I go lay my self down to sleep I feel it, but in the morning or even at night when I'm busy I don't feel a single abnormality in my pulse. It just happens when I'm going to sleep.

So vacation came, and I was at home, I never felt any of it for like a month. And when I came back here at my apartment (4 days ago), yesterday I felt the scary pulses again. I haven't sleep comfortably as I'm too anxious about it and too many things started to run on my mind whether I'm having a mild stroke or very high blood pressure or starting to have a heart disease. I'm really scared. I browsed in different websites and most of them have the same thing too and what causes them is stress and anxiety.

Help me please. I'm not asking for an accurate diagnosis but for a possible causes of this.