Almost every day. Like you said, some days are better than others, but other days, to me, are just... almost unbearable.
However, my tension is in my stomach and chest primarily. I'll also get it in my upper neck and back at times. The stomach pain is the one that's most constant. It can be a dull ache in the upper left quadrant of my abdominals (Where the stomach is located) or more in the middle (Solar Plexus). I have constant stomach issues as of lately, such as reflux that doesn't burn, but is definitely there.
During anxiety attacks my chest will tighten up... A lot. My breathing becomes shallow. Stomach aches and tenses up. All fun stuff.