When we pulled my son out of PS last year, he did the same thing. Turns out, he had post-traumatic stress disorder. He had been under so much stress at school that when we pulled him out, he basically melted emotionally. It took about a month for him to recover. I believe that is why some people "unschool" for a while. Unfortunately, I didn't have that option because our first county review was set for just two weeks later.
During his recovery month, I started with simple assignments such as making long lists (which I would scribe) about why he was special and loved. He thought that was awesome. He actually took the list with him wherever we went and would read it to anyone who would listen, like waiters, etc.
I slowly moved from there onto some perfectionist exercises. Before we would begin a game, I would say, "I am going to let you win this game." Then, I would have him practice telling me good game, good try, etc. after his win. Also, I would pout a little and ask him if I was a failure because I lost. Of course, he didn't want me to feel bad, so he would offer me encouragement. Then I would say, "Now, I am going to try to win this game." I would win the game and reverse roles on him.
This was not a pleasant exercise initially because of his perfectionistic tendences. However, after several days, it became a little easier for him. I'm not sure it would work for everyone, but you might want to give it a try. If you do, be sure to add lots of humor. It really helps take the edge off.
Last year, I had to sit with my son through every school task. It was exhausting, because I felt like I was doing the work. This year has been very different. He is more organized and willing to work independently. (Which is why I can be on this website now, while he is doing his grammar work!)
I am still a fairly new homeschooler as well, but I can tell you the rewards (after a rough start) have been amazing. I finally have my sweet, confident son back.
Hang in there...I do think you'll find that things will get better.