Fatigue will swimming

Hello all,

Today during my workout I experienced something I have not experienced before. I kind of starting feeling it before but today it happened very emphatically.

I have been training every day, around 1-1.5 Hrs per day, alternating between swim, bike and run. I also do some strength workouts twice a week. I keep a very balanced diet and eat a good amount of food.
Today I started my swimming workout with some drills, swimming 2x100 m with fits closed, then some more drills with the pull buoy, then soem other swimming in Zone 2. At the end of my training sesion, I do some endurance training and today it consisted on swimming 1000 m. However, after 150 m I started to feel very tired, my arms would not respond very efficiently, I could not take good breathes, I kept thinking on the remaining distance and I also felt mentally tired..all in all, I was a disaster in the pool. I manage to finish my 1000 m by taking some breathes at the edge and with an extremely high effort. At the end of the workut I felt like a crap, like the worst swimmer...BTW, the day before what I did was some biking in the morining for 1.5 Hrs working in Zones 1 and 3.
Let me tell you that in the past I have been able to finish the same workout with very good times and being able to swim the 1000 m continuously without stopping at the edge.
Has any of you been through this before? Is this chronic fatigue? am I training too much? Please advice, I am concerned that instead of progressing with my training I am going backwards and becoming less competitive.