Are you using a needle meant for knits? You should use a ball point needle.

I agree with Rescuer I use a Ball point needle and a special stretch knit stitch which is built in to the machine. Hope you can work it out as there is nothing more frustrating than not being able to sew. An alternative of course is to use an overlocker (serger). Love and blessings Chris

Good explanation below about Ball point and stretch needles.

That's got to be it ladies! Thank you! If I'm doing onsies-what size needle would you suggest?

RockyB, I have found throughout my years of embroidery that thread nests/bunches and needle thread breakage are usually a result of incorrect thread tension (upper or lower) and/or stabilizer. The best results I have had embroidering t-shirts is ironing a piece of fusible stabilizer to the back of the area where the design is to be stitched. Be careful not to stretch the knit when ironing on the fusible. I hoop a piece of light weight (thin polyester) cut-away stabilizer. Then, I spray a bit of K2000 adhesive spray to the fusible, and carefully align and stick the t-shirt to the hoop. Pins place out of the way of the needle near edge of hoop can help hold excess fabric, while stitching the design. I rarely ever hoop knit fabrics because of the stretchiness. The slightest stretch will cause distortion of the design and puckering. A light polymesh cut-away is needed to support stitches on knit fabric.
Hope this helps you.
Angel

welcome! great question. i've been embroidering for 6 yrs & still like to read tips about sewing knits!