For Several Months Now, My Muscles Have A Tendency To

For several months now, my muscles have a tendency to stay flexed after being used. Started in my arms, but has spread to the muscles down my sides, and on occasion, my stomach and legs. If I reach over my shoulder to scratch my back, when I bring my arm back down, the muscle stays flexed and I have to rub it to get it to relax. Not painful, and doesn't continue to tighten like a cramp, it just doesn't relax on its own after flexing. Same happened recently with stomach muscles when coughing. Tightened muscles in my abdomen when coughing, then had to rub my stomach to get them to relax when coughing stopped. When first started, thought I was staying dehydrated or something, but have been making sure to drink plenty of water and it's not getting better, it's spreading. First started in forearms, now happening along my sides, stomach, and occasionally legs. Should I worry?