Hello I believe I can help you with your concern
I am so sorry that you have been experiencing this weight gain with the Effexor, unfortunately that can happen.
Now some individuals have been prescribed Wellbutrin in addition to the Effexor. Wellbutrin is an effective antidepressant and has been shown to curb appetite and promote weight loss.
Now the issue with combining these medications is that when combined they can cause a syndrome called Serotonin Syndrome, which is very severe. This is why you cannot use high dosages when combining these two medications.
So if you are prescribed low or moderate dosages of the Wellbutrin and Effexor (You are a low dose of the Effexor right now), then you can take both medications with a low risk of developing Serotonin Syndrome.