I've been stressed lately, and because of this my breath feels short, and the back of my neck hurts, also heart pounds before i sleep, what's wrong?

Sounds like anxiety: Aches and pains, shortness of breath, and a racing, pounding or palpitating heart are common symptoms of anxiety. You correctly connected these symptoms to the stress you've been under. The solution is to either decrease the stress or learn to effectively cope with it. A prudent course is to try doing both. Talking with someone close to you and practicing relaxation techniques can be helpful.

Anxiety: Panic attacks and anxiety can make you feel this way. Perhaps seeing your doctor to rule out other causes can be beneficial? Good luck