In pain / exhausted for 2/3 days after training (supliments/stretches?)

[Reala]

I am currently having 20g - 40g carbs a day on my current diet (for refference)

[treelizard]

At least 40% of your caloric intake should be from carbs, preferably in the form of fruit or vegetables. 30% protein max. Again, make adjustments based on rule of thumb I mentioned above.

[osopardo]

would love to be able to give my all in each session...

Even my doctor has recognized a part of my personality which makes me do everything to the extreme and has strongly recommended that I ease up.
Yes, giving it your all is important, but a good coach or trainer will understand that you will have your off days and appreciate the fact that you did show up. Oh, he'll still ride you and push you to try harder, but he'll know you're recovering from the previous workout and expect you to be off a bit. Just keep at it and do your best for that day. Remember that a bad training session is better than none at all...