Hello sweetgirl1175 welcome.
I am severely under motivated also, I have a stack of mail and papers next to my desk which need sorting and filing in the bin, its been there for months, growing bigger and bigger. I also get to crisis point with washing, house-work and things like cleaning my car. In regard to my car, I was seriously embarrassed just last week, I use the floor of the front passenger seat as a 'bin' and suddenly I needed immediate help from a auto-electrician. There was no way out, he opened the door and I felt like a total pig with all the rubbish on the floor. So, I got caught out then!
I find like others have suggested that exercise does seem to help but that has gone to the dogs for three weeks. I must not let another day go by for that.
Since I have not conquered my unmotivated behaviour, I cannot offer any sure fire ways to get over it.
Please remember, University is hard, especially when you have PTSD, so be kind to yourself.
You will not be judged here, No-one will condemn or criticise you. We all have issues and most have multiple issues.
I know getting up, showering and getting out the books or going to the campus feels overwhelming, I also have that problem when I have to go to the doctor, chemist or even a short bit of food shopping. When I am done and home again, all I want to do is get into bed. Some days I get up, feel too tired, ring and cancel whatever appointment I had, and go back to bed. I just cannot face the day. This especially happens when I have multiple things to get done. I was sent to a specialist for my fatigue but there was nothing to be done, he said I had to learn to live with it.
This Forum has a lot of information regarding PTSD, you are sure to feel better when you read at least some of the articles and information on the beginning of the site.
Best wishes