I had palpitations hampering my sleep efforts at night, now a very fast pulse rate

[WorriedCat7]

So actually there are 2 occurences I want to talk about. The first one took place yesterday; near the end of a bike ride I noticed a squeezing sensation behind the sternum (might be insignificant I just thought Id mention it)  and then moments after I had finished my vision suddenly became blurry and I was feeling very tired for a minute or so forcing me to sit down and wait for it to end. To my overall state of health; I am 19 years old in decent shape, dont smoke and dont even drink any alcohol. I have never fainted in my life so this was concerning to me as I think I might have been close to it. So anyway I have also had palpitations that last for the entire night for about 1 week now. Last night I began feeling my pulse to check if it was elevated and it was not at first( my resting heart rate is 60)  but then it suddenly jumped up to a very high rate which I never experienced ( or at least caught) before, lasting for ~ 3 seconds perhaps.( at my wrist ) This felt extremely strange I dont think momentary anxiety could possibly do that as it was simply way too fast. I always thought of my palpitations being anxiety as this was what was suggested to me as the most likely culprit when I did my research online. Now one thing I sometimes get a weird very fast twitching at the side of my neck but thats muscle spams and not the pulse right? When I go to check it its already gone. Hope someone can help me here.