Assalamu alaykum,Sometimes shaytan whispers in the mind of a believer to annoy him and cause him difficulty. The fact that you don’t like these doubts indicates they are simply whispers from the shaytan and are not true doubts. Don’t pay attention to these whispers and instead focus on learning more about Islam and trying to get closer to Allah سبحانه وتعالى. There are some du’as you can read also. For more advice regarding this, please see this thread:
How to Overcome Waswasa/OCD in WorshipWith regards to depersonalisation, increase in making dhikr and reciting Qur’an, as well as pondering its meaning. In addition, consider getting help from a psychiatrist.