I have been on Zoloft forever. I take 200 mg per day. I take 2 pills (100 mg each) every night. However, lately immediately after swallowing one pill I get TERRIBLE nausea and sometimes I vomit (more like dry heave). I am not taking them on a empty stomach. It is usually after dinner. Because of this, I hardly ever get to take the 2nd pill. What could be causing this after all this time?