Hi flanisha, I am so sorry to hear of your loss.
I was looking at this forum for the first time as I also feel like I have no idea how to get through this situation.
My dad died six weeks ago from renal cell carcinoma, which had spread to his bones and lung. It was just under seven weeks from diagnosis to death and he was just 66, only retired for less than a year.
I feel for you regarding your mum, it seems natural to feel helpless that there is nothing you can do to ease her pain or loneliness. I don't know about you but I've also felt guilty when I talk about my fiancé because I know she is suddenly alone and never imagined she would be in this situation.
I think what you are doing here, looking for helpful advice, support and allowing yourself to talk and grieve is a good thing to do. The fact that you're even aware of mood swings when going through this shows how much you care for your husband and I'm sure you are his number one priority at the moment.
I really hope you are starting to find ways to celebrate your dad, grief seems to come and go in waves where I remember all over again it's not a bad dream. Other times I have already started to smile when I think of family jokes or funny memories, it is still so soon but I hope your tears will start to be replaced by smiles and fond memories some day.
Wishing you all the best hun, feel free to private message me if you like, I felt like we had a lot in common reading your post.
Anne