when you are preggo you get all types of unknown harmless pains it could just be your body adjusting to your pregnancy but if it is constant i would def go see your dr. congrats!!
If it is on your right side you'll want to see your doctor ASAP as it could be your appendix. At 7 weeks you shouldn't be experiencing pain that high up from pregnancy as your uterus is still tucked under the pubic bone and hasn't grown large enough to cause that kind of discomfort just yet.
I developed gall stones during my first pregnancy. I had pain in my upper stomach, right in the center. Mine started later in my pregnancy, so I just thought it was the baby pushing on my ribcage. I ended up having to have my gall bladder removes 2 weeks after giving birth. From what I understand this is very common during pregnancy. Your pain may not be from this, but I just thought I would mention my experience to you. Good luck.
It could just be heart burn - it can be extremely painful, and is very common in pregnancy right from the start. Try taking some gaviscon or some rennies and see if it helps with the pain.
Oh, and your appendix is very low down on your right hand side, towards your pelvis, so don't get too concerned about that.