Upper ab pain?

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I’m 36 weeks today and I’ve had horrible upper ab pain the last week, especially when I lay down and get back up. If I’m up & moving I’m fine, but during the night I’m up multiple times with the sensation that my upper abs (like right above my bump) are being ripped apart & my upper stomach is rock hard. I know Braxton hicks can be different for everyone, but why does this only happen when I’m laying down & get back up?