Mental stress ( sorry if it's too long )

These days I feel really really exhausted all the time due to school and my parents academic pressure , I know they want the best for me but it's really exhausting to the point I am not able to even give a small laugh , September 6 is coming soon , last year I lost someone who was really dear to me ; my cats.. They told me "it's just a cat" "move one" yet they didn't console me..I might be selfish saying that. But they don't know how happy they made me , And i blame myself for abandoning them , my father hated my cats and thinking that I wasn't able to do anything for someone who gave me so much happiness hurts , I started to isolate and went into depression because after all that my friends started to talk behind my back , i tried venting to my mom but she told me I had suffered nothing and I am overreacting as a teenager....And whenever she tells me to work , I am just so exhausted I am unable to do it and then she calls me a useless child , and tells me the "you don't love me" line, I am holding so much in me that idk how to feel anymore, and i believe the probelm is me cause I see all kids my age be happy..but deep inside I don't feel happy at all.. I just want someone to understand me and be there for me...