The same thing happened to me 2 weeks ago. I took three pills (which were mdma, not speed)at roxy. At the end of the night, my heart started to feel like it was beating out of my chest, I couldnt breath well, and I had chest pain. This got progressively worse as the next day went on, and at around 8pm I was sure I was going to die. I felt like I was going to faint, could barely breath, and my heart was beating really fast. My boyfriend drove me to the emergency room where they told me that my heart was okay, and I didnt need to worry - just rest. For the whole next week I was home in bed with horrible chest pain and trouble breathing. I was really scared because I had gotten plenty of rest, and it was still there. It eventually got better and better.. but the whole experience upset me so much that im not going to do stimulants of any kind ever again.. its just not worth it to me anymore