Feeling Guilty About My Mother's Death

I feel like I have officially lost it.... I was laying in bed tonight and I looked up and saw my mother standing in my door way... my mother passed away when I was 6... she just stood there for a few moments until I woke my husband up to see if he saw someone there too and he didn't see anything... I have always felt guilty because of my mother's death because I was so young and it was very confusing for me. she had a heart attack during my brothers soccer game and I thought it was my fault because I didn't want to sit with her at the game I wanted to go with my dad to the park... I thought I broke her heart and deep down I feel like it's still partly true... what do I do I took my meds but I can't sleep