That's terrible :( Nightmares can plague you and drain all your energy let alone affect your mood. I had a recurrent one for about 5 years but it lessened over time. I found it heightened when I was struggling with issues during the day irrespective of what they were. Thankfully now I rarely have nightmares but I can appreciate how they don't start your day off well.
You mentioned you can't afford therapy - here is Australia, irrespective if you are religious or not, some of the churches offer free or subsidised counselling with a trained professional. You often have to wait for a turn but after an incident which lead to the police charging my now ex, I went and saw one and I was blessed with a lovely lady who helped me get through a terrible time and she also had a few appointments with my son to make sure he was okay. Are there any such resources where you are?