Dear Emma,
What kind of resolution in this situation are you looking for? You mentioned about being upset and having doubts about the relationship that you have with him. In the 12 months since the incident how has his behavior been? You mentioned that he had written messages that contained horrible things being said about you. Has he behaved in a way that makes you think that he is still likely to do the same.
When distressing thoughts are there the tendency is to group all negative things in life along with that. It may be better if you can treat this situation in isolation and take a look solely at the relation that you have with him and where you want to go with it.
Don’t think of yourself as a common denominator to all the previous relationships. It always takes two for a relationship to be in a particular way. I am certain that you are neither nasty nor horrible.
Your child is still small and needs you to be closest to being at your best possible state of mind. Hope you are able to work yourself towards that.
Take care