I have been suffering from withdrawal symptoms since I stopped taking Venlafaxine. How many days can these symptoms last?

Hello, I was prescribed Venlafaxine about two and a half years ago for anxiety and depression. Since the beginning of the summer, I agreed with my doctor to gradually decrease the medication (I was at 300 mg). Since 2-3 days, I have completed the last step of the decrease (I was then taking one 37.5 mg capsule per day). However, I do not feel very well, I am very dizzy, I have nausea and I have sensations of shocks in my whole body. I know these are withdrawal symptoms, but can they be so bad that I have to go back on the drug to function better? And how many days can it last? Thank you in advance for your help.