Anxiety, low blood sugar, or something worse?

So about a month ago I went to the hospital because I felt like I was about to pass out my heart was beating really fast I was feeling really dizzy and light headed and it felt like my heart was skipping beats upon arriving I started to become very shaky and unaware of a lot of things before I had smoked weed but haven’t since I figure it’s not worth it and wanted to start living right and then a couple weeks later at work the same thing started happening but not as worse I just became a little light headed was shaky and notice my heart was beating fast to the point where I had to be sent home from work a couple people told me to check my blood sugar and i have been monitoring it a couple times it has dropped below 20 and then it normal stays at around 70-90 I have also noticed my heart beating really fast from doing the simplest of things or nothing at all but what had made me ask all this is on top of that today at work I noticed a pain in my chest for like a couple seconds and then it was gone following that I started to worry and My left shoulder blade was hurting and also my jaw a little bit and my throat felt like it was closing in and it became harder to breath i have had problems with my shoulder for a while but never got it looked at sometimes it feels all tingly and numb and others it’s like a sharp pain on the shoulder blade when I go to touch it it always feels a little sore some with certain areas of my chest I went to a heart doctor about 3 years ago and they said everything was fine I just have a irregular heart beat and I have went to the hospital twice and they have never told me anything was wrong with my heart they have always discarded me with something called tachycardia so I guess what I’m trying to ask is it heart attack? Anxiety? Low blood sugar? Or maybe just a mix of low blood sugar and me worrying to much about other health problems any help would be nice especially to just put me at ease 

Also forgot to mention that like a lot of the times when this happened I just worry a lot and I feel like numb every where for a couple seconds also along with the chest and should pain sometimes when I breath in there is a little popping sound 

Also heat flashes