This is not OK. You are being bullied in the workplace and it has to stop.
Have you got someone at work to go along with you to HR, where you need to make a formal complaint in writing?
Even before going back to HR, you need to write down everything you can remember that has happened with this manager. Take lots of time in your evenings to do this and recall everything you can. Then take these with you to HR and make your formal complaint.
Do you have a union? If so, get onto your rep and tell them what’s happening. If you don’t, that’s OK as you can contact a union and join one, even if there is not one in your workplace. Get onto union websites for your type of work area.
I strongly suggest you go to your doctor to record this with them also.
You are not in your place of work to be treated this way. You are probably right in saying you are an easy target for this bully because you are a quite person. Bullies always pick on quieter people, whom they believe will be easy targets, but now it is time to stand up for yourself!
It is not good for you mentally or emotionally, to allow someone to treat you like this. This person is breaking a number of employment laws and you need to know this. This will help you to make the stand for yourself that you need.
I also recommend you talk to a solicitor, you may need legal support, especially if the HR department is unsupportive. MDM are one group of solicitors who specialists in this area.
The Citizens Advice Bureau, a free service, is also very helpful.
But the main thing you need now is good personal support to help you be assertive and stand up for you.
Please also check out if the company have internal counselling services for their staff. This may be through an EAP programme which is called Employee Assistance Programme for staff.