So sorry to hear about the loss of your dad, Mani. It is early days for you. It was a long time for me to start to feel anything like in control of my life and myself after losing my mum. I remember the first six months were terrible and it was a long hard slog over the next 18 months to fins a way forward at all. It does get better very slowly and the pace of change is different for everyone, so don't expect too much of yourself and just take things one day at a time.
I had questions after my mum died too and anxiety, I am sad to say, is part of the shock and devastation of loss. Loss is one of the hardest things we ever have to deal with and there is no right or wrong way to do that. I found it helped to speak to the doctors and find out more about why my mum became so severely ill so suddenly. She was gone six weeks later. Understanding did help. Doing something about things also helped, but at the end of the day, nothing can fill the void losing someone so close to you leaves behind and you simply learn slowly to live with the sadness and grief becomes a part of you. Over time, it does retreat into the backgound and the happier memories come to the fore again, but it is always there and so you have good days and bad, but you just have to try to find your way forward one day at a time. Try to be kind to yourself and do whatever makes that at all easier along the way and you gradually learn to iive your life again, but it is hard.
You are not alone. Everyone who has ever posted on this site, will know what you are going through, but we all eventually have to find our way forward. Talking really does help, so seek counselling if you can and don't be afraid to say whatever you want here. We will all relate to what you are feeling and someone will have some wise words to say that might help you too.
Wishing you well.