I don't want to post a specific medicine on a forum. Except maybe Ibuprofen if you have taken it before and know who to take it (its very harmless... but you can't take one every 5 minutes :/).
BUT, a way to alleviate very bad tummy aches is to lie with your tummy facing down in a comfortable bed. It's not 100% effective, but it helps A LOT when the pain is really bad, and you are waiting for the medicine to do it's job. It can be effective by itself, but this depends on the type of ache, and it's rare.