Sarah asked 3 months ago

I truly appreciate this forum you give for us to ask questions.
When I was not Muslim, I was advised to place my savings in A CD account. I did not know interest was haram at that point. I would have invested my money in something halal back then.
This was 10 years ago, and I cannot find the starting investment and the bank does not still hold the original files.
Now that I know it is haram, I have cancelled the use of the CD but cannot find the calculations of the interest earned, except for the past 3 years.
I would like to donate the interest, but I cannot figure out how much interest has been earned and it has been making me feel so guilty and miserable. I wish I knew then what I know now. 
What can I do? Since I did not know, can I donate the interest from the past 3 years, then separately donate zakat as well? Then pray for forgiveness inshallah?
I feel so terrible. 
Thank you.