Very uncomfortable

I wake up and get up to use the br
All of a sudden while I'm standing and walking I'm unable to stand straight up 
I have this (I want to say) "cramp" feeling in the middle of my back going around to my belly a little
And my belly feeling tight
It almost feels like so much gas
I don't know how to explain it 
FTM- sorry 
It is so uncomfortable 
Anyone knows what it could be? 
29 weeks