Yes and No. Yes they are real and no they are not your thoughts. I have schizophrenia and hear voices for 4 years. I have also practised Vipassana meditation for 15+ years and professionally I am a telecommunications software and electronics engineer.

I see this phenomenon clearly as demonic interference. I know that OCD thoughts are also intrusive thoughts generated due to the presence of demonic entities in your space. Basically they are voices generated due to their presence. That is why they are dark and unpleasant. It has nothing to do with your anxiety – your anxiety may be making it easier for demons to be in your presence. But the content is not generated by you.

Please read my answer here for auditory hallucinations in schizophrenia that details how this phenomenon works- I have specifically mentioned what OCD thoughts are and how they are generated. Basically schizophrenia is a big superset of OCD.

Can thoughts turn into auditory hallucinations

How can I get rid of OCD myself?

I would recommend the following 3 things-

1. Ask a teacher permission to sit a 10 day Vipassana course by S N Goenka in a centre near you (www.dhamma.org).They will teach Anapana meditation for 3.5 days in the course that helps us become observant and accepting of our thoughts. Thoughts are just thoughts and this can be achieved by focusing on our breath and not following the thoughts. It is a very simple technique and a very powerful meditation that teaches us how to be mindful and detached towards our thoughts.
2. Do not identify with intrusive or compulsive thoughts that you don’t feel comfortable with. As soon as you hear a thought that is weird or feel a compulsion just assume that it is not you. You may or may not believe in demons but intrusive thoughts are often caused by entity attachments – the thoughts generated due to that connection are not our thoughts or our karma. This is actually more common than we know. So we shouldn’t bother about “those” thoughts at all. No need to get disturbed- all is fine. Just accept it and be diligent about keeping a practice around it.
3. Bring more breath based practices like Pranayam etc into your daily routine. Breath creates a distance from our thoughts and gives us space to be more vigilant and equanimous to outside stimulus.

I think also getting help from a therapist, can be very helpful.