Pains during pregnancy

I’ve been hurting all day and I’m wondering if it’s normal. It’s not a sharp, shooting pain and honestly it doesn’t even hurt its more just uncomfortable. It’s low in my abdomen and keeps switching sides depending on how I’m positioned. This may sound gross but it feels like I need to let out the biggest fart of life but nothing’s happening. Is this normal for first trimester because it’s got me worried? I have an ultrasound appointment tomorrow which already has me nervous and I can’t help but worry that somethings wrong.