vavanopi8355-san,
I'm very sorry for your loss...
Well, I'm not very sure how I should translate "i should be here from the beginning".
Do you mean you wish you were there from the beginning? Are you going to say that to relative's family or
someone close? If my understanding is right, it'll be
初めからそばにいたかったです。hajime kara soba ni itakatta desu.
This literally means "I wanted to be next to you from the beginning".
But assuming you're posting this comment (instead of saying it face to face),
初めからここにいるべきでした。 hajime kara koko ni iru beki deshita.
This also should be fine. This means "I should have been here since the beginning".
If you could tell me better about your intention or feelings/messages you want to write, I might be
able to help you better.
And, "in the past ive Done my best to answer your questions " would be
いつも、あなたの質問に答えられるよう最善をつくしてきました。itsumo, anata no shitsumon ni kotaerareruyou saizen o tsukushitekimashita.
Literally, "I've always tryied my best so that I could answer your questions".
Hope this helps
Natsuko(奈津子),
Team JapanesePod101.com