Myles had some cramping once we upped his dose too. He didn’t seem to have them with the low dose, but maybe that’s because he was so miserable all the time that I didn’t notice.
I did notice some cramping when we upped his dose to to 30 mgs. I was worried about it but I read here that some babies react to the aspertame or lactose and that they usually adapt in about two weeks, so I stuck with it and sure enough the cramping stopped in about two weeks. 
Hopefully that’s all it is with Logan, but I do wonder if it’s reflux that’s bothering him. 7.5 mgs twice a day is still a pretty low dose. And for Myles the cramping from his Prevacid usually only lasted 30 minutes to an hour after taking his solutab. I’m not sure why it would last all night long.