The first thing is to take a break, get a Diet coke. THEN: Clean and oil it really good. Sew a few simple squares together for a test run (also in case there is oil). Then, if it is still not behaving, run (don't walk) to a repair shop for a tune up.
I firmly believe that frequent cleaning and oiling makes a huge difference. My machine is 34 years old, and has been to the fix-it show maybe 2 or 3 times total.