I have experienced ego death on both LSD and Mescaline. Bottom line is this. NOBODY can tell you what ego death aka break through aka ALL YOUR BODY SENSES SHUT OFF is! There simply aren't enough words to accurately describe it. You can only understand by experiencing it. I can, however tell you some key points that will let you know definitively whether or not you experienced this.
The FIRST time is likely to be terrifying. As your mind begins to let go of the "self", "you" frantically attemp to keep control of "reality". Once you lose control and "reality" gives way to truth, all the fear transforms to peace, contentment and understanding.
During this time, ALL of your senses are disconnected from the mind. You will see clearly, but not through the eyes. You will hear everything, but not from the ears. You will feel all, but not from the flesh, etc.
Also during this phase of your journey, time dilation may be so great that hundreds of years will pass in the period of less than an hour Earth time. In the course of these years you may experience several lives, deaths, reincarnations, etc.
Regardless of all else the SINGLE thing that defines a breakthrough experience like ego death is this. You will have NO concept of "self". You won't know who "you" are or even have a concept of "you". You won't even have the vague concept that "you" may be a human! The experience will be pure experience without the bias of seeing anything from anything's point of view. You will experience without the crutch of an experiencer and discover the lack of separation between everything, the infinite continuity of all into all.
Like I said, great people far more eloquent and articulate than I have failed to describe ego death with mere words, simply because it's not possible, but I hope my brief summary has at least helped a little to illuminate the reality of your experience.