What Causes Lighter Periods, Stomach Cramps And Acidity?

I am having menses every month without fail, but during this menses period my flow of menses is nt good as it only last for 2 days & also very bad upper tummy cramps like gaseous feeling. Its very unbearable pain and also having lower back pain. But all these pains and menses last for two days after that back to normal. I am more worried for the gaseous tummy during my menses than the irregular menses. Is there any solution how to keep away from the gaseous stomach