Possibly you can have any combo, but have you been diagnosed?
Diagnoses like these are labels used more for insurance reimbursement and pharmaceutical patent purposes than for helping the patient. Basically, anxiety is anxiety, but the different labels are there because treatment can be different for some based on either controlled experiments or FDA approval for drugs. For example, the treatments for PTSD include some that are pretty specific to that diagnosis than it would be for GAD, which has more general treatments. For example specifically, PTSD has some research showing rapid eye movement treatments can help, which doesn't mean they can't help other anxiety disorders, it just means somebody did some research on it for PTSD. Similarly, marijuana is generally considered a no no for anxiety sufferers, but it has shown some benefit for PTSD sufferers. The problem with these diagnoses is that they are very often incorrectly given and patients adopt the labels as their identity, perhaps making it harder to get better. So yeah, you can have lots of diagnoses at the same time -- most anxiety sufferers also suffer from depression and often the cause is the depression -- but that doesn't change the fact that your problem is obsessively thinking about things in a way that makes your life miserable and the treatment always tries to change that. I have multiple diagnoses as well, but they're mostly anxiety categories. So don't focus so much on the label, focus on finding something that changes the way you're thinking about your life.