I'm having a really bad stomach ache since last night...I took 2 motrin IB 200mg each 2hrs ago and planning to take zantac (ranitidine) now, can u do that?

Yes. It is okay to take the zantac, but be careful with the ibuprofen. Depending upon the cause of your stomach ache ibuprofen can make it worse. If you need something else for the pain take tylenol (acetaminophen) instead. See your doctor if the pain does not go away soon.