what the hell is wrong with my shoulder?!

samco66

i tried to workout today but it was a complete FAIL. first i tried to run but every time i took a breath in through my nose my forehead burdened like a b**ch which was causing a horrible headache, it was like i was breathing in -20 degrees air. So i tried to do my arms, the second i tried the machine where you pull the bar down toward you it felt like my muscle was popping out. It was the muscle that is on the top of my left shoulder right below my ear ( close to my neck). it feels like there's a knot on my shoulder/ lower neck area and its popping out every time i pull the bar down and it hurts like hell. i didn't get to workout over the weekend because my legs hurt so i was realllly excited to workout today, now i just feel like a failure and im pissed off like no other. what is going on with my shoulder? i have been doing this workout now for 4 weeks