Contractions only at night?

So starting last week I began to wake up and feel a lot of pressure very low that was painful, it almost took my breath away. I was freaked out the first time it happened and called off work the next day. I asked my OB about it at my 38 week appointment this past Friday and he said it’s most likely contractions, but my question is had anyone else only gotten them in the middle of the night? He said I could be feeling them more then due to being dehydrated from sleeping. Anyone else have anything like this?