stress can cause some of your symptoms, sure. how much sleep are you getting during the night? that has a huge factor in how you feel during the day. how much water do you drink? do you consistently change your workout routine? if not, you may be hitting a plateau. change it up! try to do a 3 day program like DC, 5x5...etc to give your body 4 days of rest. sounds like you just need rest. also, you may want to try to take a week off from the gym. see how your body feels during the week.