Kvod Harav. I have been having problems lately. I feel as if I am making vows in my head that have negative implications on me and if I do not perform a certain task immediately or very soon after this negative outcome will occur. Further, as I was praying amidah I found myself making what I think is a neder by saying I will try and refrain from mixing meat and milk in my kitchen, however once I realized I re started amidah because I did not want the negative thought I have associated with this vow to happen If I do not keep this neder any advice?
It sounds like you are having a really tough time balancing your growth with negative feelings when you don’t get it right. It is often difficult to find the line between healthy spiritual growth and obsessive guilt and shame for a lack of it. It is good to strive to be the best we can, to grow in all areas of our lives, but if the push for growth is having a negative impact on you, it is not a good type of growth. The Torah is דרכיה דרכי נועם, its ways are that of pleasantness. The path to God should not be one of misery and perpetual guilt.
If one finds themselves making vows often that have a negative impact on their life, these vows do not come from a religious place. Such vows do not have the status of a neder, and one has no obligation to uphold them.
You would be best finding a Rabbi or mentor who is more familiar with you. They will be able to guide you on a healthier path.
Best of luck