How to get over the loss of your father.?

My father passed away on February 24 of this year. My dad was my best friend, a mentor, and hero to me and for the past almost two years my dad had quickly deteriorated to nothing but skin and bones by the hands of motor neurone disease. I was his only son and I just turned 15 a few weeks ago so ever since I was about 12 this has been happening. I watched as my dad went from being the strongest man I knew to a man using a cane, then to a walker, to a wheelchair, and then to the point where he couldn't get out of bed. I had to do things no kid should have to do. I am living now with regrets that I didn't do more with him while he was with me. Im even starting to give up on my religion seeing as ive always been good and prayed every night while my dad was sick for him to get better. I don't know why God didn't help him get better I just don't know. But now im just really upset over everything has happened I know just by this little description im only brushing the surface on what has been the last about 2 years of my life but now im just asking how can I get over his loss its just draining me of my energy. I just finished my finals even though my dad past only a few months ago so now im even more exhausted then ever. I need some help on what I can do to get over his loss and at the same time I need some sort of an answer why God did this to me please help me, thank you.