Antidepressant and diet pill

I take Zoloft and recently started taking Mega Green T diet pills. I noticed the box said don't take with prescription drugs. Is there any reason I shouldn't mix these two together?
Also about 3 days into taking the diet pills I started having abdominal cramps and nausea, which isn't anything new to me (I have a bad stomach) so I'm not sure if it's related to the diet pills or not. Is there anything in Mega Green T pills that would cause these symptoms?