There are different types of fish oil out there. I'm not an expert, but you have to look at how much EPA and DHA the actual capsules have in it. One higher than another could be causing your problem. I've been on fish oil for about two years and have yet noticed any kind of differences on how I usually was before taking it. In fact, your the first I've heard of this issue. I use to take the Sam's 1200 mg fish oil, but recently switched to Walgreen's, Finest Natural, as they had a buy one, get one free thing going. Stuff ain't cheap.