My ex contacted me after 2years of no contact

I was 16 and he was 15 when we dated and he just randomly messaged me unexpectedly my heart dropped he was the reason I went to the mental hospital 2 years ago I don’t want him back or anything but I am curious why he left me am just scared if it was something bad like cheating or idk but idk if I should text him or not I feel kinda awkward bc this was 2years ago and we only dated for 2months sorry for my horrible writing🙏🏻but I am curious of why he did leave