I think it's bad posture/form and too much weight. Keep your back straight, look forward not down at your arms , and keep your chest up and shoulders slightly back. Lower the weight, and use PERFECT form always.
Mikhail Koklyaev wrote:Benedikt he is deadlift god , I'm only amateur
Sounds like a trip to a chiropractor is in order. If you can't, get yourself one of those foam rollers and "slowly" move your spine of over it. You'll hear a few cracks but that's okay. You third choice is to get a massage, but a chiropractor is still your best bet. Even if you don't have insurance, most of them have some kind of payment plan. Remember, you can't put a price on your health.