I recently signed up with a personal trainer again, after four years of not having one. And I just started working out again with cardio and weight training. I was menstruating yesterday and began having some mild cramps and I have read that working out helps alleviate cramps. But after doing some cardio for about 25 minutes I began to feel the most intense cramps I had ever felt. I was in so much pain I had to sit down and bend over, yelping in my extreme discomfort. After I went home yesterday the cramps were terrible for the rest of the evening. Today I am not menstruating anymore and didn't have any cramps. I went to the gym today after about 40 minutes of cardio and I thought everything was fine. But now about 20 minutes later, the cramps are starting up again and they are really painful. I don't know what to do... I am in so much pain. I tried putting a hot towel on my lower belly, but nothing seems to work. Why am I having this pain and how can I prevent it?