Been having lower stomach pains for several days now comes and goes but when it does it's more so in the evenings been on lansoprazole almost 4weeks for acid reflux. what could be causing this?

Number of things: Hard to pin down from this, really. You could be fighting a virus of some kind (any loose stools or diarrhea?). You could be fighting stress (sometimes our stomachs react to stress in our lives). Could be something you're eating or not eating. I wouldn't likely blame it on the lansoprazole. See your doc if it continues past a week or so or sooner if you have the above symptoms longer than 5-7 days

See your physician: Without knowing your medical history, nor the ability to ask you questions and examine you it's not possible to give you advise as to the causes of your specific symptoms. For patient information on causes of abdominal pain see: http://bit.ly/10RdXop You need to see a physician for an exam to diagnose your problems(s). Please don't try to diagnose yourself via the internet, you won't be able to.