bless your heart. could it be that initially there was a lot to sort out so you were busy thinking about other things. if not were you perhaps still running on adrenaline & being on a high from ending such a toxic relationship. because if everything has settled down now there is going to be room for thoughts about your ex. i know it can seem crazy when you find yourself missing someone who was abusive but if you were trauma bonded to your ex then there will definitely be cravings. and i agree it can seem impossible ever trusting anyone again but its probably only because of how badly we were treated & our pain is still very raw
healing is so very up & down so those feelings of worthlessness will pass. just try to accept its rubbish right now knowing that tomorrow or the next day or the next week you will hopefully be feeling much more positive. you will be ok. big hug from me x