What is a nervous breakdown?

in my twenties i went through a really bad time and i couldnt sleep for months it was the most scariest time of my life. I couldnt think straight had no friends and had lost my job i had been taking drugs for a while and lost contact with these people who also worked beside me i walked out. I was hanging out with a girl who was i beleive mentally ill as she was strange but as she was my only friend apart from people who were taking drugs when i walked out on my job i never contacted these people again but it was really difficult for me as these people were my identity and when i lost them i felt i lost myself . T o let you understand i was always a good girl who never rebelled at school but as i got older i rebelled i started going out at weekends all the time it was a time when some people i knew took drugs but i never touched them till i was in another job where at first i didnt fit in as i was so quiet and they were the oppisite. I guess it was a mixture of curiosity as id never done it before and fitting in to be a part of something (like i said i had only one crazy friend) i really did enjoy the experience but at times i overdone it i was scared for my life thats when i decided to not do it again i didnt even have a dependancy on the drugs it was just being popular and feeling part of that type of group as at before i felt a bit square as id never done things like that my mum didnt have a clue but after walking out on job i still had high feelings even though i wasnt taking any drugs it was like i was still acting the way i was when i was and the way the people were. But it was the worst time for me as i felt i had nothing no job no friends nothing. I was finding it very difficult to sleep i guess i began to not trust myself id been reading self help books i ended up seeing a duff guy who treated me badly he slept with me and was really nasty after i ended up telling my mum as i used to tell her everything and she pure flipped saying i was stupid. I felt really alone as i had no friends and at the time felt my mum hated me she treated me with distain ib felt really ashamed of myself. She then tryed to help me as i was so depressed by making suggestions but they all felt no good as i was so low i went with one of her suggestions as i didnt know what to do i wasnt sleeping at all she asked what i wanted wiv my life my carrer i could only think of one thing so she suggested i c a friend who i hadnt seen for ages and turn up at her door now i didnt feel comfortable wiv this as we hadnt spoke in a while and i wasnt really sure i wanted to but as i felt all my decisions were going wrong i didnt trust myself and felt i needed her inpact. i was nervous all the way b 4 i went 2 c her as she is a judgemetal person when i did get 2 her house i was so uncomfortble i didnt know how to be myself i started spraffing on like the way i did on drugs trying to seem ok but it was so uncomfortable i left early as i was walking down the road i felt this fear inside of and this question inside my head "who am i?" and i felt so lost and scared when i got home i felt weird i didnt even feel right round my family it was like in that split second i didnt know who i was felt i didnt feel close to my family i felt they were strangers like i felt paranoid and didnt know how to speak to them after this episode i couldnt sleep for months and i dont mean a few hours here and there i mean LITERALLY DIDNT SLEEP A WINK! I talked with my mum eventually telling about this and that i thiught something was wrong with me she told me if i think like that there will be but anyways i learnt ways to block my feelings out being scared for no reason but i feel my life i live is just taking each day as it comes but feel its going nowhere i fear this may happen again i just wondered if that was a mental breakdown or what caused all this i have went to the doctors and i hve been put on tablets for depression but i dont know if they understand the full extent. i dont know if the reason 4 rebellion was my mum was so strict and she always tried to tell me what to do and what to say or if its for that reason i had felt i couldnt tust my own decisions and the one time i tryed i screwed up. I STILL live at home even though im in my thirtues and worry it will happen again and i cant cope