Hello - I'm no super expert, when it comes to machine quilting, however, this is how I would proceed - unpick what you have done and put your quilt aside for a little. From what I can see, it looks like your stitch length is really small, from what you describe, your tension is in need of adjustment. Make up a "play" sandwich using similar thickness fabrics and battings to your quilt...then mess about with that and get it spot on before putting that quilt near the machine (this will save much hair tearing and unpicking). You may wish to check your walking foot is fitted/engaged properly and that your machine is lint free, threaded correctly and good to go. Walking feet are not designed for speed, so maybe that could be an issue, and let the machine do the work, don't pull the fabric through, just guide with your hands. Work from the middle out and smooth and check the underside as you go (sorry, I'm not very good with describing sometimes!).
I am sure other board members will be able to help, so persevere...and happy quilting.