Sending a welcome hug
Please dont listen to those insensitive comments from your boss. It appears they have never lost a loved one and therefore cannot comprehend what it is like. You do not need to feel any guilt for your colleagues, that is your managers job to manage, not yours. He gets paid to manage the workloads and issues. Unfortunately people who havent lost people find grief messy and just dont understand. We do not get over it in a few weeks and its not all fine once the funeral has happened. Often we can look fine on the outside but our minds may be fragile or in turmoil. Work is important but not more important than your health and family.
I know that getting back to work, when we can, is good for us in a way - helps to provide structure and in some ways keeps our minds occupied which can help if we are really missing our loved ones. A phased return can help us get back into it without feeling overwhelming. You will however perhaps need understanding when you are back, perhaps have a chance to get away for a break if emotions come over you. (I remember randomly bursting into tears at my keyboard a few times!) so its good to think of somewhere you can pop off to for a break, even if its in the toilets. I went through a phase after a while of getting quite angry/frustrated and reacting in ways i didnt recognise as myself, thankfully my boss was understanding and i got through, regaining a sense of me again. I wonder if there are any useful information booklets which you could give to your boss to help them understand prior to your return, I'll have a think if i know of any. In the meantime I am guessing your Dr has given you a sick note, so you know it is supported. So concentrate on yourself and your family now. If your work are not supportive perhaps your Dr can support you with a phased return to work when you are ready
It also doesnt help that often we can feel guilt feelings during grief - 'should have's and what if's'. That is unfortunately quite a normal step, and we find we blame ourselves for things we had no control over
Everyones grief is individual to them, but people here will understand the different phases and emotions. Please keep talking to us, grief can be a rollercoaster journey, I imagine your dads accident was a shock too. You need to remember some TLC for yourself too, dont be too hard on yourself xx