I'd like to join Sophie_M and Keeeks84 in welcoming you here. They have given good advice and yes, please do give Griefline a ring. It won't answer everything but may say something that helps.
It's surprising what does help and where it comes from. My first wife spent 9 months in hospital before she passed away. I was there all that time and it was one of those situations where a decision has to be made to turn things off. I always felt guilty from then on even thought I knew it was the only caring thing to do.
Mare recently someone said to me "Look at it this way, you are taking some of her pain on your shoulders". Now that really has helped - another person's wisdom.
So like your dad, and now you mum, you have a whole load of images of them in your mind, images of their lives drawing to a close. I was the same.
Other images will come, as new events in your life 'paper over' your grief with fresh problems, wins and losses. The good as well as the bad memories will emerge. I can picture my wife and I laughing, or more properly trying to keep straight faces as we teased a kid. I enjoy that memory unreservedly now.
There is no set timescale for greif, and also the talk of there being a number of stages is all very well, but not that accurate - everyone is different.
Do you have other family members, siblings or friends, you can talk with and let them listen, not trying to fix things or make suggestions, just leaving you feel cared for.
Going it alone is extra hard.
You do not have to get the old me back, that person is still inside you, the go-to person people went to to get thing fixed or get help is inside you still, and it will re-emerge. Your help will be all the better as you will understand more of life's trials.
Try to find the times you shared in happiness, not easy right now I know, but let those images mix with the ones in your head now. That's where I'm at and I'm happy, though can still feel sad sometimes at the loss.
Please let us know how you go