medication

Whilst I have no knowledge of ADHD, I gather there are some that are sometimes prescribed to help with concentration. 

There are no medications for autism, because it isn't an illness.  All autism and ADHD mean is that your brain is structured differently to most people and you think in a different way.

However, it could be that you develop a mental health condition because of the difficulties in living as an autistic person or ADHDer in a world not designed for us.  The only thing that a psychiatrist would prescribe for is if you have such a mental health problem. 

I really wouldn't advise self-medicating because some medications for mental health issues can do you a lot of damage if you don't actually need them or you end up taking something for a condition you don't have instead of the one you might have.

If you are depressed or anxious, your GP can diagnose those conditions and prescribe anti-depressants, but if it is anything like psychosis only a psychiatrist can prescribe.  I understand where your GP is coming from.  He/she needs to know for sure whether you are autistic or not, whether you are ADHD or not and whether you have a mental health condition beyond everyday depression or anxiety or not.

You might be able to get some other support in the meantime though if you talk to your GP.  Different regions might be different, but in our areas MIND CASS run short courses for people who are waiting for an assessment or have just been diagnosed.  The also offer advice and guidance on all sorts of topics and run an informal peer support network for autistic people.  Your GP might also be able to refer you for some counselling in the meantime, but if so, do make clear that you are waiting for an assessment as the therapist will need to make adjustments to the approach.

I would go see your GP again to see what he/she can do while you wait.

Whilst I have no knowledge of ADHD, I gather there are some that are sometimes prescribed to help with concentration. 

There are no medications for autism, because it isn't an illness.  All autism and ADHD mean is that your brain is structured differently to most people and you think in a different way.

However, it could be that you develop a mental health condition because of the difficulties in living as an autistic person or ADHDer in a world not designed for us.  The only thing that a psychiatrist would prescribe for is if you have such a mental health problem. 

I really wouldn't advise self-medicating because some medications for mental health issues can do you a lot of damage if you don't actually need them or you end up taking something for a condition you don't have instead of the one you might have.

If you are depressed or anxious, your GP can diagnose those conditions and prescribe anti-depressants, but if it is anything like psychosis only a psychiatrist can prescribe.  I understand where your GP is coming from.  He/she needs to know for sure whether you are autistic or not, whether you are ADHD or not and whether you have a mental health condition beyond everyday depression or anxiety or not.

You might be able to get some other support in the meantime though if you talk to your GP.  Different regions might be different, but in our areas MIND CASS run short courses for people who are waiting for an assessment or have just been diagnosed.  The also offer advice and guidance on all sorts of topics and run an informal peer support network for autistic people.  Your GP might also be able to refer you for some counselling in the meantime, but if so, do make clear that you are waiting for an assessment as the therapist will need to make adjustments to the approach.

I would go see your GP again to see what he/she can do while you wait.