20 weeks - Anyone else feel mild cramping when they standing for sometime ?- TMI pics , pls read below

So this has started happening recently after 20 weeks where I’m feeling mild period like cramping in lower abdominal region after standing for few mins. Like 20 mins or so. I’m a little worried if this is normal. Also I had very very little brown discharge noticed 2 times when I wiped and had like a small brown and white tissue like mucus in the toilet bowl. I feel the baby move so that’s comforting but still wanna know if this all normal ?

Had anatomy scan a week before and it was normal. All this has stopped for last 24 hours but still paranoid as the mild pain is still there . I’m going for ultrasound today to get this checked out.