Are you using a ball point needle? That could be it or if you've sewn over pins you may have a burr on it and it will need to be changed no matter how new it is.
As far as the stitches you've got a tension problem. Try lowering the upper tension a tiny bit at a time. If the loops are fairly large it's your bobbin tension. Your bobbin may not be wound tightly enough or the tension somehow has gotten wonky. Be very careful when adjusting a bobbin tension, the tiniest adjustment may work just fine.