How DOES being pregnant physicaly REALLY feel?

Sarah
Hello,
I'm in my 14th week and I feel strange in my belly...
Appart from some mood swings and occasional nausea, I also feel weird and uncomfortable physicaly...
I am mostly sedentary, at home, and everytime I change position, get up, sit, go up the stairs, etc, I feel a weird sensation in my belly. 
I imagine the baby is wobbeling inside of me, but am I suppose to feel it so much? 
I feel "pulling" sensations around my belly. Is it my skin and muscles extending? My organs moving? The baby wobbeling? I feel like this everyday, all day, since a few days. Also kind of if I had a water balloon inside of me moving around. And I feel tense around the belly area, and very sensitive...
I've had an echography a week ago before these sensations started and everything was fine. My next check-up is due mid-Jan. 
I'm a bit worried and wonder if all this is normal. Am I suppose to feel so uncomfortable so soon?
This is my first pregnancy so all this is very strange to me and I don't know what to expect... I'm also getting more and more emotional and anxious...