Past Traumatic experience. For me now?

Last year before Diwali, i witnessed a very stressful event which was very uncomfortable, shocking and couldn't believe on what happened. My mom had heart attack for two times in span of 4 days. She recovered via angioplasty but her wellness didn't brought life back in me. I Started having panic attacks at night and sleepless night and that continued for 2-3 months atleast. I didn't seek any professional help because i didn't wanted to take any medicines. I started recovering slowly with time. Gone through various mood troubles and cried hard whenever i felt. Although today i am able to sleep and eat well but I still find the event disturbing. I feel like something is wrong with me. I feel like my psyche has been affected somehow . I feel the frustration at times. I don't understand what is troubling me deep down inside. I tried various ways to process my emotions but i think i am failing at that. What should i do to heal my past? Is professional help necessary for me now?