Page 43 of your sewing manual for the Espire discusses heavyweight fabrics. Those seams should glide through the machine.
Your presser foot lift lever should have 2 position levels. All the way up for thicker fabrics, or seams in your case, and halfway for thinner fabrics. Your machine also has an Automatic Fabric Sensor. This should be turned 'ON'.
If you have used your needle for hours prior to the point you are at now, it may be good idea to change out your needle. Cheap trade-off to eliminate frustrations and to sew smoothly.