Daniel Smith, from Rochdale, was just 21 when he was commended for his brave actions in Iraq. But he has since found it difficult to get treatment, his marriage has failed and he is struggling to find work.
For a number of nights each week, Mr Smith parks in a lay-by and sleeps in his car, to get away from people and control his anger management issues.
"I just don't like being around people sometimes I just want to close myself off. Basically I don't like living on people's sofas, I am not relying on people to put up with me. When I am depressed I would rather be alone so I've just got used to doing it now," he told the Victoria Derbyshire programme.
"I have got my quilt and stuff in the back and I have got my internal wifi here so it's like a mobile house."
It is thought Mr Smith's PTSD was sparked after the vehicle patrol he was part of was blown up by roadside bombs twice in a week in 2005.
The medically trained fusilier tried to help many of his colleagues who had received terrible injuries.
"I took a lot of guilt because obviously I thought I did my best at the time when I was treating them. I didn't really think they would die, I just thought they would be injured or go back home, but they passed away and obviously that was a big shock to us and I didn't know how to take that," he said.
"I became a bit scared then. I didn't know what to think or what my next step would be. Because it happened to me twice and I thought it will happen to me third time unlucky."
The Ministry of Defence citation when he received his medal said: "With no regard for his own safety and with his focus firmly on saving those in the vehicle, he commenced the evacuation of the casualties from the burning chaos."
What is PTSD?
Post-traumatic stress disorder is an anxiety disorder caused by witnessing or being involved in a frightening or distressing event.
People naturally feel afraid when in danger, but the legacy of some traumatic events is a change in perception of fear.
They may feel stressed or frightened in day-to-day life.
Diagnosing PTSD
But Mr Smith, now 31, blames himself for not being able to save his friends and does not think he deserves the medal. In fact, he does not really remember being awarded it by Prince Charles.
"I didn't really take it all in, I was very numb that day because I was on medication anyway so my mood and my temperament wasn't the best," he says.
Figures from veterans' mental health charity Combat Stress show Mr Smith is not alone.
It has seen a 28% increase in veterans seeking mental health support from April 2014 to 2015, treble the 9% increase seen the year before. Almost 6,000 are registered with the charity, and it says it has never been busier in its 97-year history.
Mr Smith says he got good treatment at first, with six weeks of intensive therapy, but it tailed off, leaving him frustrated and bitter. Eventually he got a medical discharge from the army.
His marriage failed because of his anger, which also caused him to lose his job as a bailiff.
"At the time I was blown up I didn't really think it would affect me. It didn't feel reality at the time but a year later it had time to sink in, your depression kicks in, you're drinking. You don't realise you are changing, but other people see you are and you just become very angry towards them," he explains.
His father, Gary, says he has been "pushed from pillar to post" since leaving the army and the family has so far spent over Â£3,000 to try to get him diagnosed and treated.
"Basically all they have done is put a sticking plaster over a gaping wound and just sent him into general society to pick up the pieces which is really difficult, because society doesn't pick the pieces up from remnants of the army," he says.
"There was no follow-up from the NHS, there were no papers handed over from the military to the NHS to follow on his treatment."
His father says he worries about his future, as without treatment or a support network he thinks a long-term recovery is unlikely.
And Mr Smith says he is bitter about how he has been treated by the army. "I feel like I have been cast aside until the next person comes along because I haven't done anything wrong," he says.
The Ministry of Defence said it did not comment on individual cases. But it said: "The government is absolutely committed to the mental health of our armed forces and provides a wide range of support both during and after service.
"We work closely with other government departments and agencies so that where necessary, there is continued effective treatment and support on transition to civilian life."
Watch the Victoria Derbyshire programme on weekdays between 09:00 and 11:00 on BBC Two and the BBC News channel.
Better support is needed for members of the armed forces who leave the military with Post Traumatic Stress Disorder (PTSD), one of the youngest recipients of the George Medal has said.