I have that alot... Its from stress
, and not taking care of ur self. Heres something that u should try. I do it maybe 3 times a day. Go to a quite spot. Either your room, under a tree, where ever u are comfy at. Sit indian style and take your right hand and wrap it under your left wrist. Grip it until u feel your heart beat with 2 fingers. Close your eyes and consentrate on that heart beat. Dont think any bad things. Think of things that are peacful to YOU! Do that for 3-5 mins. then stop thinking and put your mind on your heart beating. Now think of your heart beat slowing down. By doing this u can slow your heart rate
down enough so that u will be okay. Make sure that during the day you are drinking enough water... if u dont like water drink tea but the idea is to not have so much Caffine. It sounds like u might have Anxiety
attacks and those are no fun some doctors try to give medicine for it but I dont take meds of ANY kind and never have. I have learned how to handle it. Try also taking time out for YOU every day. that means Alone... take a walk, pray, read, do whatever u like to do. I like to paint or do art. Find something that u enjoy doing and do it alone. If your problem get worse tho, u might wanna do see a doctor if ur into that kinda stuff.Personally Im not... but thats just me. Good Luck and I hope you feel better.