Hi and welcome to DWD. I'm glad you've seen your GP and that you have some kind of a plan in place. Remember that any antidepressant takes anywhere around 4 - 8 weeks to get into your system, then the same time for each dosage change and for stopping. Currently you have at least some of each of 3 meds - with side effects of starting and stopping in your system, hence why you are feeling rough...
What I will say is that my husband's story is similar to yours and actually venlafexine has been amazing for him. Are you sleeping?
You can get through this and you deserve to be happy.
Keep talking.