I swallowed top permanent retainer. Yesterday, and today my stomach does hurt. Is it That I should've, and now go to the doctors?

Yes. I would recommend that you see a doctor if you are having stomach pain. An xray may be ordered too to evaluate the location of retainer and see if there are any signs of stomach damage.
ER. If you are having pain you need to be evaluated immediately to determine location of the retainer in your GI tract and to evaluate for bowl perforation. Usually small (2 tooth) appliances work their way out without problem. Larger (4-6 tooth) appliances are more problematic. Seek evaluation now.