Essential fatty acids make me weak and tired :(

I hear all the time that essential fatty acids are good for you. One thing I hear is that they can improve your cardio and muscle recovery, but for me that's not true. If I eat fish, spiurulina, or EFA supplements more than two days in a row I loose all my stength and I can barely run without feeling fatigue. Actually the first day I'll try them I'll feel great, but it wears off and then I feel like crap. I really am curious why this is. I always made sure the fish was from a clean area, bought certified organic spirulina, or bought EFA supps from fish caught very deep. I did't overdo it either. Just last week I only ate fish (no other efa foods) a few times and still I noticed the effects. I guess I have to stay away from EFA's but I have no idea why I get this reaction. Anyone know or know where I could find out?

thanks,
Perry