Why do Omega 3 capsules increase my anxiety?

A year and a half ago I was taking Omega 3 supplements which amounted to 1200 mg of Omega 3 fatty acids a day and for a long time this greatly benefited me, it alleviated depression and anxiety etc. But recently whenever I take Omega capsules of any amount (even 300 mg) my anxiety shoots upwards and my problems become a lot worse. The weird thing is, whenever I eat raw salmon instead of taking the capsules I don't feel an increase in anxiety at all and salmon contains a significant amount of Omega 3 fatty acids. I've tried different brands and they all have the same negative effect upon me. If it's an allergic reaction to the capsules then how come I didn't feel the adverse effects a year and a half ago when I started taking them and if its too much Omega 3 then how come I don't feel any adverse effect when I eat salmon instead of taking the capsules?