I just started working out a little over a week ago. Jogging a mile every other day, crunches and some ab workout videos. Also started a plank challenge around the same time. After a few days, my stomach was sore to be expected but since then, I've been getting these weird stomach cramps that lasted a few days. All day yesterday, my stomach felt fine until I jogged a mile at lunch. About an hour later, my stomach feels tight right under my navel and there is this consistent dull ache. I slept fine last night but it has been there all day today. Can this come from working out?