There are two different problems here. I am a 15 year old boy. Fairly active.
1) In the past, this happened quite often but it stopped. Now the problem is coming back. There is this short but very painful pulsating/throbbing pain on the left side of my back neck. It feels as if its a artery or something going to burst. It lasts for 2-4 seconds and each second it will pulsate twice (on,off,on,off). I checked up the anatomy of the neck and it seems to be around the middle to top of the Trapezius muscle.
2) Time to time there are sharp pains in my chest. The location can vary. It could be on the side of my chest or around my heart. It feels like a large needle is stabbed in. Breathing in hurts it more and I have to hold what remaining breath I have for 10-15 seconds.