I don't know why you would not immediately suspect a form problem. I would.
1. Form needs to be evaluated
2. Be more conservative with your increases
3. Sometimes you can set up back irritation for a deadlift with your presses/bench beforehand, eg relaxing into overextension with press or bench. IOW, #1 for all lifts and/or experimentation with moving bench/press away from the deadlift.
4. Are you using a belt?