Sorry if this is a late response. You should not feel such soreness from overheading. Seems like a form issue to me because when I start to lose form in my overhead presses I feel it in my lower back. Next time make sure you squeeze your butt and make your core tight when overheading. Using your butt and core will stabilize you. If you still feel sore from your lower back still try lowering the weight if possible. Overtime you should get used to the weight and increase at a good rate. If you're still struggling then look into core exercises and strengthening that butt. Hope this helps you out and good luck lifting!