Dittoing the others. Most likely you just hurt your shoulder somehow, but at 7 weeks it can be a sign of an ectopic pregnancy. Just a case of better safe than sorry, as Emsy said!
Call your doctor right away, they will examine you and if necessary you'll get a scan to be sure that all is well.
Try not to let this panic you, it's just sensible given that your shoulder hurts. Bet you wrenched it somehow, but the doctor will still be glad that you came in
