Felt scared when i saw deceased person in casket?

I went to my aunts (mom’s sister) funeral today. My aunt passed away to last stage Leukaemia cancer she was 67 years old. When I was close to the casket I felt scared my heart started to beat fast so I let my brother go ahead of me to lay down a flower petal in the casket then it was my turn to put the flower petal in the casket. I was too emotional. I started crying when the funeral started and when they took my aunts casket to the crematorium. This was my second time at a funeral I was too little to remember seeing my grandpa’s funeral. 

After the funeral was finished, I started having a bad headache. How am I going to get rid of this thought? I should have prepared myself to see a deceased person in casket. Maybe I have Necrophobia phobia.