I had the same problem you had, I put alot of pressure on my self and when I went out to bat, instead of playing to get runs, I played not to get out. As soon as that happens, you are doomed. I always worry about what people think of me, which can be really stressful and would result in me basically giving up in the nets after one bad shot, because I thought I looked bad and people were laughing at me. It didn't help that they would bowl with plastic balls to be fu**heads, but I had to get over this as it was just weighing me down. I am also an opener and had scored 400 runs the year before, but for some reason, this year I batted 6 or 7 and only opened the batting 3 times, which really upset me as I didn't understand why I wasn't opening. Plus I was really a yo-yo in the season just gone, just going up and down and not having a set place in one set team. Not all bad as I got to play 2nd grade, but still really frustrating. It was deffinately the first year, in my 10 year's of playing, that I have not enjoyed my cricket.
In the nets I was always working hard and my goal was not to get out, and I was sucessful at this. But one day one of our older players told me I was being too defensive and told me to just play my shots and swing through the ball to get my confidence back, effectively treat it like a T-20. I did this and I felt so much better, as I was confident if I went hard that I would clear the field even if I miss hit it, which was a big concern for me. This then translated to the pitch, with scores of 65 and 43 in the finals. Not the best scores, but still good considereing I was really struggling. Plus I also hit my 2nd legitimate 6 and it was 89 meters, which was insane considering I have only hit 1 previous to that and it was only around 50 meters
One piece of advice our club selector gave me was "There are already 11 people on the field trying to get you out, don't make it 12", really simple but that helped aswell. My advice to you would be to really have a go in the nets when you bat, as it doesnt matter if you play a bad shot as you are simply trying to get your confidence back. Net form isn't the best indicator for a good game, but it certainly helps with your mindset and confidence, and they are just as important.