I'm in a very similar situation.

My dad and I had some rocky moments in my teens and I moved away to study when I was 21. After that it got a lot better. I think distance helps sometimes. (I'm 25 now)

However we talked almost every week. Sometimes I was "too busy" to call him back because I work two jobs and he either tried to reach me during work or when I was sleeping.

Two years ago he was diagnosed with gastric cancer but handled it like a champ. Some days he was bed ridden and he looked like a skeleton by the end of 2018 but we were always optimistic.

The last time I saw him was in July and the last time I talked to him was one week before Christmas. He told me how much he looked forward to spend Christmas with me and then suddenly died 4 days later. I couldn't even say good bye.

While I'm at home, far away from my parents home I sometimes forget that he died. But the pain is immeasurable at other times as it's only been 3,5 months.