Will try not to drip feed, so this may be long winded.
DD is 5.
Bit of a back story, last year, another parent (lets call her Mother A) approached me and told me that DD was part of a group of girls who had been bullying her DD (all aged 4 at the time). She made it clear that my DD wasn't the bully, but she was involved in upsetting her DD. Mother A was very confrontational, rude, intimidating and generally very, very unpleasant towards me. It left me very shaken.
The whole thing came as a massive shock to me. I had no idea at all about what had been going on.
I spoke to the head the following day, who confirmed there had been allegations against my DD (6 months previously), school investigated, and found no problems with regards to my DD. All other issues had long been sorted and settled. Head said that parents are called in when school have exhausted all other channels. Both Head and DDs teacher felt there were no issues with DD which is why I wasn't' contacted.
Head was incredibly annoyed that mother A had approached me and dragged up the situation.
Fast forward to this September. DD was coming home almost daily telling me she was getting told off for something in school. e.g, for not listening, pushing another girl, shoving someones bag, shouting at a girl, pinching someone etc.
After a month of this, I wrote a letter to DDs teacher stating my concerns that DD wasn't behaving in an appropriate manner in school.
She wrote a letter back to me saying that there had been an issue with one of the girls in class feeling unhappy about coming to school. The head had spoken to DD and her peers about the importance of being nice friends. The teacher had said girl in question was happy again and all issues had been resolved in school and there was no concerns with DD at all.
Several weeks later, it was parents evening. No concerns from teacher. She said DD does get a telling off at times, but no more than any other pupil in the class. She said there were no issues with regards to her friends, or any one being unhappy. She was happy with DDs behavior and general school progress.
Fast forward to now, and DD still sometimes comes home saying "X was crying in school today because I pinched her. I had a row from Miss Y and then I was crying" and general issues like that. Pushing, shouting at other children etc.
I'm finding myself loosing control of my paranoia towards DDs behavior in school. I'm worried she's a bully that all the other parents warn their children about. If I'm honest, I think Mother A has left me a bit traumatised and paranoid 
Every time I contact the school, they reassure me. I'm starting to feel like an over bearing annoying parent.
I reenforce heavily to DD the importance of being nice. The consequences of her actions, we do reward charts and sticker charts to encourage her.
We both talk about how being nasty can upset other children and the importance of thinking about other children's feelings and emotions. We talk about these issues at length during bed time.
She seems to genuinely understand, then the following day she'll come home saying "I had a row today because I pinched X"
This afternoon she's come home from school saying she shouted at X and upset her 
I just don't know what to do.
I don't go to school myself mornings/afternoons due to other circumstances, DD has transport to school, so I don't get that regular daily contact with school. I worry sometimes I fill in my own blanks and end up in a mess like I am now.
Please be gentle with me, I'm at absolute rock bottom 