Hi
Welcome to the MedHelp forum!
There are three main possibilities—angina, gastric reflux and pinched spinal nerves. The best thing would be to consult a general practitioner or PCP and try and assess what is the cause of your problem. Then proper referral for concerned specialist can take things further and get you proper treatment. Take care!
I've taken muscle relaxers before and I felt the same way that you did at first! I took them at night before bedtime. They are great when used that way! If it continues, it might not be a bad idea to see your regular dr. He might order an MRI of your spine/neck. Best of luck!
Mine do that sometimes and it takes several massages around the shoulder blades and the neck. Also my chiropractor helps very much. Not the old timey one that "cracks" your back, very up to date doctor. He has also used a combo of muscle stimulating machine that sticks on your back in certain areas with cold and warm packs placed on my back and it does wonders.